Added "." on to check_dtype and obj parameter
- [] closes #xxxx
- [] tests added / passed
- [] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [] whatsnew entry

From #28602
`pandas.testing.assert_categorical_equal: Parameter "check_dtype" description should finish with "."
pandas.testing.assert_categorical_equal: Parameter "obj" description should finish with "."`