BUG: AttributeError when read_sas used with GCS
With GCSFS (and when a binary file buffer is passed in), the output from
the file read is `bytes`, not a Unicode `str`. The `encode` call is unnecessary
in this case.

- [x] closes #33069 
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry
