isort 5.0 UserWarning about `--recursive` flag

[Zymergen-jvandezande]

As of isort 5.0 (released July 4, 2020), the --recursive flag is no longer necessary. Adding results in the following warning:

/home/runner/.local/share/virtualenvs/spectra-KcgPObjh/lib/python3.9/site-packages/isort/main.py:1206: UserWarning: W0501: The following deprecated CLI flags were used and ignored: --recursive!

While not pressing, this should probably eventually be removed from .github/workflows/test.yml