added test for replace with value none
- [ ] closes #46606
- [ ] Added test to pandas\tests\frame\methods\test_replace.py
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).

Hello @VladislavYarovenko! 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/tests/frame/methods/test_replace.py`](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py):

> [Line 1489:5](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1489): [E303](https://duckduckgo.com/?q=pep8%20E303) too many blank lines (2)
> [Line 1490:5](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1490): [E115](https://duckduckgo.com/?q=pep8%20E115) expected an indented block (comment)
> [Line 1490:5](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1490): [E265](https://duckduckgo.com/?q=pep8%20E265) block comment should start with '# '
> [Line 1491:33](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1491): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1491:35](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1491): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1491:44](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1491): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1491:46](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1491): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1492:31](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1492): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ':'
> [Line 1493:39](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1493): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1493:41](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1493): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1493:50](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1493): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','
> [Line 1493:52](https://github.com/pandas-dev/pandas/blob/ee3330eee7b7668949e1cdc5e76bccee1d917b7d/pandas/tests/frame/methods/test_replace.py#L1493): [E231](https://duckduckgo.com/?q=pep8%20E231) missing whitespace after ','

 thanks @VladislavYarovenko for the PR. I'm not sure we need to add a test to close https://github.com/pandas-dev/pandas/issues/46606, just changes to the docs? This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. thanks for the PR @VladislavYarovenko, but has gone stale if you wan to continue, pls ping.