DOC: Add SA01 for `pandas.api.types.is_string_dtype`
xref https://github.com/pandas-dev/pandas/issues/58577
fixes  `-i "pandas.api.types.is_string_dtype SA01"` in [`ci/code_checks.sh`](https://github.com/pandas-dev/pandas/blob/c468028f5c2398c04d355cef7a8b6a3952620de2/ci/code_checks.sh#L657)
Thanks @tan-i-ham