BUG: is_dtype_equal(dtype, "string[pyarrow]") raises if pyarrow not installedimport error resolved
- [x] closes #44276
- [x] tests added / passed
- [x] 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
- [x] whatsnew entry

Added instance to check string preventing import error
