Update multiple instances of `dtype_backend` parameter description to make them all consistent
- [x] closes #53878
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).

Note that this supersedes PR #53881.
/preview Website preview of this PR available at: https://pandas.pydata.org/preview/54104/