Fix the @xfail_if_ci pytests in `test_soundcard.py`

[cclauss]

This pytest xfail should be removed:

SoundCard/test_soundcard.py

Line 10 in a5cc715

xfail_if_ci = pytest.mark.xfail(os.getenv('CI') == 'true', reason='Testing on GitHub Actions continuos integration')

The GitHub Actions tests that use this decorator should be fixed on Linux, macOS, and Windows.

• Add a GitHub Action to run pytest #200