ENH: add string method remove prefix and suffix, python 3.9
Opening this issue for discussion:

Since python 3.9 is out, and we have the new [string methods](https://www.python.org/dev/peps/pep-0616/) `removeprefix` and `removesuffix`, it would be nice to add them to the pandas string methods as well
```python
In [2]: import pandas as pd

In [3]: df = pd.DataFrame({'A': ['str_string1', 'str_string2', 'str_string3']})

In [4]: print(df)
             A
0  str_string1
1  str_string2
2  str_string3

In [5]: df['A'].str.removeprefix('str_')
Out[5]: 
0    string1
1    string2
2    string3
Name: A, dtype: object
```
An argument not to add this is that it's pretty easily to achieve with `str.split`:
```python
df['A'].str.split('_').str[-1]
```
