Warnings from package building

The 0.4.0 publish action is pointing out some warnings originating from `setuptools`:
See

https://github.com/astropy/asdf-astropy/actions/runs/4471646987/jobs/7856805781#step:7:729

It looks like:
https://github.com/astropy/asdf-astropy/blob/b3dafcc8e4f400ec667ba538b9f156d4c5279e6f/pyproject.toml#L62
may be misconfigured.

I believe the the documentation for this is in: https://setuptools.pypa.io/en/latest/userguide/package_discovery.html#package-discovery-and-namespace-packages

Start with pyproject.toml around line 62 and inspect the warnings in the linked 0.4.0 publish action, especially the setuptools package-discovery documentation referenced in the issue. Determine which configuration is producing the warnings and verify the package build completes without them.

Written by the indexing model from the issue text.