Move Unit Test GitHub Action back to ubuntu-latest

[tig]

In #2927:

Based on this, I moved running the test to windows-latest instead of ubuntu-latest. Tests now pass.
microsoft/vstest#2952
Sheesh.

My opinion is that when that vstest issue is fixed then change it again to ubuntu-latest again because normally Windows users forgot to test in WSL first to detect conflicts before pushing them. Don't you think?

I agree. FWIW, the tests DO sometimes fail for me now under WSL:

So, this might just be a bad test on our part.

Originally posted by @tig in #2927 (comment)

Related: #1316

Once #2927 is merged, and we can diagnose why the tests are failing under Linux, we should change back.

[tig]

I just spent 3+ hours trying to figure this out.

No joy.

FWIW, it fails on macos-latest as well.