Cleanup in hist.py
Found a small typo in hist.py

Hello @Gowthami-R! Thanks for opening this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:

* In the file [`pandas/plotting/_matplotlib/hist.py`](https://github.com/pandas-dev/pandas/blob/324239c8a7f00dba1af1febe794e43e32f8f02ce/pandas/plotting/_matplotlib/hist.py):

> [Line 249:89](https://github.com/pandas-dev/pandas/blob/324239c8a7f00dba1af1febe794e43e32f8f02ce/pandas/plotting/_matplotlib/hist.py#L249): [E501](https://duckduckgo.com/?q=pep8%20E501) line too long (91 > 88 characters)
> [Line 403:53](https://github.com/pandas-dev/pandas/blob/324239c8a7f00dba1af1febe794e43e32f8f02ce/pandas/plotting/_matplotlib/hist.py#L403): [W291](https://duckduckgo.com/?q=pep8%20W291) trailing whitespace
> [Line 512:1](https://github.com/pandas-dev/pandas/blob/324239c8a7f00dba1af1febe794e43e32f8f02ce/pandas/plotting/_matplotlib/hist.py#L512): [W391](https://duckduckgo.com/?q=pep8%20W391) blank line at end of file

