BUG: 1.2.5 -> 1.3.x breaks yaml.dump(DataFrameObject)
- [X] I have checked that this issue has not already been reported.

- [X] I have confirmed this bug exists on the latest version of pandas.

- [ ] (optional) I have confirmed this bug exists on the master branch of pandas.

---

#### Code Sample, a copy-pastable example

```python
import pandas as pd

tmp = pd.DataFrame(
        {'col_name': [1,2,3,4]}
)

import yaml
dumped = yaml.dump(tmp)  # Fails starting with pandas==1.3.0
print(dumped)
```

#### Problem description

Another package, [pytorch-lightning](https://github.com/PyTorchLightning/pytorch-lightning), has the option to save all given hyperparameters. They yaml all given parameters, which resulted in the kind of ugly output shown in the expected output for dataframes. Starting with `pandas==1.3.0` this breaks because of the MWE shown above. 

If this is expected behaviour from pandas I am sorry, then the issue should go to pytorch-lightning probably. 

#### Expected Output

<details>

        !!python/object:pandas.core.frame.DataFrame
        _flags:
          allows_duplicate_labels: true
        _metadata: []
        _mgr: !!python/object/new:pandas.core.internals.managers.BlockManager
          state: !!python/tuple
          - &id004
            - !!python/object/apply:pandas.core.indexes.base._new_Index
              - &id002 !!python/name:pandas.core.indexes.base.Index ''
              - data: !!python/object/apply:numpy.core.multiarray._reconstruct
                  args:
                  - &id001 !!python/name:numpy.ndarray ''
                  - !!python/tuple
                    - 0
                  - !!binary |
                    Yg==
                  state: !!python/tuple
                  - 1
                  - !!python/tuple
                    - 1
                  - &id003 !!python/object/apply:numpy.dtype
                    args:
                    - O8
                    - false
                    - true
                    state: !!python/tuple
                    - 3
                    - '|'
                    - null
                    - null
                    - null
                    - -1
                    - -1
                    - 63
                  - false
                  - - col_name
                name: null
            - !!python/object/apply:pandas.core.indexes.base._new_Index
              - !!python/name:pandas.core.indexes.range.RangeIndex ''
              - name: null
                start: 0
                step: 1
                stop: 4
          - - &id005 !!python/object/apply:numpy.core.multiarray._reconstruct
              args:
              - *id001
              - !!python/tuple
                - 0
              - !!binary |
                Yg==
              state: !!python/tuple
              - 1
              - !!python/tuple
                - 1
                - 4
              - !!python/object/apply:numpy.dtype
                args:
                - i8
                - false
                - true
                state: !!python/tuple
                - 3
                - <
                - null
                - null
                - null
                - -1
                - -1
                - 0
              - false
              - !!binary |
                AQAAAAAAAAACAAAAAAAAAAMAAAAAAAAABAAAAAAAAAA=
          - - !!python/object/apply:pandas.core.indexes.base._new_Index
              - *id002
              - data: !!python/object/apply:numpy.core.multiarray._reconstruct
                  args:
                  - *id001
                  - !!python/tuple
                    - 0
                  - !!binary |
                    Yg==
                  state: !!python/tuple
                  - 1
                  - !!python/tuple
                    - 1
                  - *id003
                  - false
                  - - col_name
                name: null
          - 0.14.1:
              axes: *id004
              blocks:
              - mgr_locs: !!python/object/apply:builtins.slice
                - 0
                - 1
                - 1
                values: *id005
        _typ: dataframe
        attrs: {}

</details>

#### Output of ``pd.show_versions()``
`pandas 1.2.5`:
<details>


INSTALLED VERSIONS
------------------
commit           : 7c48ff4409c622c582c56a5702373f726de08e96
python           : 3.8.10.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
Version          : 10.0.19042
machine          : AMD64
processor        : Intel64 Family 6 Model 158 Stepping 10, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : de_DE.cp1252

pandas           : 1.2.5
numpy            : 1.21.1
pytz             : 2021.1
dateutil         : 2.8.2
pip              : 21.1.3
setuptools       : 52.0.0.post20210125
Cython           : None
pytest           : 6.2.4
hypothesis       : None
sphinx           : 3.5.4
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.6.3
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 3.0.1
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : 2021.07.0
fastparquet      : None
gcsfs            : None
matplotlib       : 3.4.2
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : 1.6.1
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : 0.51.2

</details>

`pandas 1.3.1`:
<details>

INSTALLED VERSIONS
------------------
commit           : c7f7443c1bad8262358114d5e88cd9c8a308e8aa
python           : 3.8.10.final.0
python-bits      : 64
OS               : Windows
OS-release       : 10
Version          : 10.0.19042
machine          : AMD64
processor        : Intel64 Family 6 Model 158 Stepping 10, GenuineIntel
byteorder        : little
LC_ALL           : None
LANG             : None
LOCALE           : de_DE.cp1252

pandas           : 1.3.1
numpy            : 1.21.1
pytz             : 2021.1
dateutil         : 2.8.2
pip              : 21.1.3
setuptools       : 52.0.0.post20210125
Cython           : None
pytest           : 6.2.4
hypothesis       : None
sphinx           : 3.5.4
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.6.3
html5lib         : 1.1
pymysql          : None
psycopg2         : None
jinja2           : 3.0.1
IPython          : None
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : 2021.07.0
fastparquet      : None
gcsfs            : None
matplotlib       : 3.4.2
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : 1.6.1
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : 0.51.2

</details>