CI/TST: Use pytest.mark.skipif instead of marker for CI clipboard tests
- [ ] 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

Allows us not to have to always set the clipboard marker and will just skip those tests if not available in CI tests.
Looks like when determining the clipboard in the CI it tries to probe the clipboard in a crashable way. This approach doesn't work. Closing.