BUG: DataFrame.rank() wrong result for inf
- [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.

---

**Note**: Please read [this guide](https://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports) detailing how to provide the necessary information for us to reproduce your bug.

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

```python
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randn(3, 4))
df.iloc[0, 0] = np.inf

df
          0         1         2         3
0       inf -0.614812 -0.316211 -0.049311
1  1.254238 -0.082490 -0.199442 -0.373851
2 -1.440219  0.723572  0.028726 -0.904849

df.rank()
     0    1    2    3
0  NaN  1.0  1.0  3.0
1  2.0  2.0  2.0  2.0
2  1.0  3.0  3.0  1.0

df.iloc[0, 0] = -np.inf

df.rank()
     0    1    2    3
0  1.0  1.0  1.0  3.0
1  3.0  2.0  2.0  2.0
2  2.0  3.0  3.0  1.0
```

#### Problem description

as you can see, -inf and inf get different results.

#### Expected Output

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

<details>

INSTALLED VERSIONS
------------------
commit           : 3e89b4c4b1580aa890023fc550774e63d499da25
python           : 3.8.5.final.0
python-bits      : 64
OS               : Linux
OS-release       : 4.15.0-118-generic
Version          : #119-Ubuntu SMP Tue Sep 8 12:30:01 UTC 2020
machine          : x86_64
processor        : x86_64
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8
pandas           : 1.2.0
numpy            : 1.18.5
pytz             : 2020.5
dateutil         : 2.8.1
pip              : 20.3.3
setuptools       : 51.0.0.post20201207
Cython           : None
pytest           : None
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.6.2
html5lib         : None
pymysql          : 0.10.1
psycopg2         : None
jinja2           : 2.11.2
IPython          : 7.19.0
pandas_datareader: 0.9.0
bs4              : None
bottleneck       : None
fsspec           : 0.8.4
fastparquet      : None
gcsfs            : None
matplotlib       : 3.3.3
numexpr          : None
odfpy            : None
openpyxl         : None
pandas_gbq       : None
pyarrow          : None
pyxlsb           : None
s3fs             : None
scipy            : 1.4.1
sqlalchemy       : None
tables           : None
tabulate         : None
xarray           : None
xlrd             : None
xlwt             : None
numba            : 0.52.0

</details>
