BUG: histogram plot ignores `xlabel` and `ylabel` arguments
- [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 numpy as np
import pandas as pd
data = pd.Series(np.random.random(10))

##problem
data.plot.hist(xlabel="My xlabel", ylabel="My ylabel")
```
 Output graph:
![wrong](https://user-images.githubusercontent.com/6746316/116669303-b4e89380-a99e-11eb-9c80-e601b2516b87.jpg)



#### Problem description
The method accepts the keyword arguments but ignores them and overrides them with defaults (respectively <nothing> and "Frequency". While those defaults are sensible, specifying those keyword arguments should either be met with the intended output (custom x and y labels) or an error (of the type `NotImplementedError`)

The documentation (for [hist](https://github.com/pandas-dev/pandas/blob/2cb96529396d93b46abab7bbc73a208e708c642e/pandas/plotting/_core.py#L1266) and [plot](https://github.com/pandas-dev/pandas/blob/2cb96529396d93b46abab7bbc73a208e708c642e/pandas/plotting/_core.py#L680)) seem to indicate this is supported (although a bit unclear)

#### Expected Output
The outputted graph should be the same as when produced with the following code:
```python
import numpy as np
import pandas as pd
data = pd.Series(np.random.random(10))
ax = data.plot.hist()
ax.set_xlabel("My xlabel")
ax.set_ylabel("My ylabel")
```
Which is the following:
![fixed](https://user-images.githubusercontent.com/6746316/116672092-0d6d6000-a9a2-11eb-842f-44966ff83550.jpg)

#### Output of ``pd.show_versions()``

<details>

```
INSTALLED VERSIONS
------------------
commit           : 2cb96529396d93b46abab7bbc73a208e708c642e
python           : 3.9.4.final.0
python-bits      : 64
OS               : Linux
OS-release       : 5.11.0-7614-generic
Version          : #15~1618626693~20.10~ecb25cd-Ubuntu SMP Thu Apr 22 16:00:45 UTC 
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 1.2.4
numpy            : 1.19.2
pytz             : 2021.1
dateutil         : 2.8.1
pip              : 21.0.1
setuptools       : 52.0.0.post20210125
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.6.2
html5lib         : None
pymysql          : 1.0.2
psycopg2         : None
jinja2           : None
IPython          : 7.22.0
pandas_datareader: None
bs4              : None
bottleneck       : None
fsspec           : None
fastparquet      : None
gcsfs            : None
matplotlib       : 3.3.4
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : 1.6.2
sqlalchemy       : 1.4.7
tables           : None
tabulate         : 0.8.9
xarray           : None
xlrd             : None
xlwt             : None
numba            : None
```

</details>
