Unpin pytest in edx-platform
Description
In https://github.com/edx/edx-platform/pull/20728 we are having to pin pytest to < 4.6.0 to work around some errors in `common/lib/xmodule/xmodule/tests/test_resource_templates.py` on pkg_resources calls. Looks like pytest switched from pkg_resources to importlib-metadata here: https://github.com/pytest-dev/pytest/pull/5063/files so I'm guessing it accidentally did some setup for us that we might need to do ourselves now?
Specifically it seems to not know the loader type to use. Here is an example error:
Steps to Reproduce
None
Current Behavior
None
Expected Behavior
None
Reason for Variance
None
Release Notes
None
User Impact Summary
None
Done
Your pinned fields
Click on the next to a field label to start pinning.