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 https://github.com/gui-cs/Terminal.Gui/issues/2927#issuecomment-1858861616

Related: https://github.com/gui-cs/Terminal.Gui/issues/1316

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