DEPR: inplace kwarg in rename_axis
- [ ] closes #xxxx (Replace xxxx with the Github issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

milestoning as 1.5 (since I assume that we would have liked to have had this deprecation in before 1.5.0rc0?) > milestoning as 1.5 (since I assume that we would have liked to have had this deprecation in before 1.5.0rc0?)

also discussion in https://github.com/pandas-dev/pandas/pull/48131#pullrequestreview-1077945769 is probably relevant to the decision here

cc @jorisvandenbossche 