Run CI Tests on macOS

[xsebek]

The CI looks like it is running tests on macOS, but they are skipped:

haskell-language-server/.github/workflows/test.yml

Lines 77 to 83 in c0f7d4c

	# Mark which GHC versions on which platforms we want to test.
	include:
	# Test all supported versions, but only on ubuntu and windows
	- os: ubuntu-latest
	test: true
	- os: windows-latest
	test: true

Is there a reason for that?

[michaelpj]

We have historically had a problem with a) tests being flaky and b) tests taking a long time. So I suspect we removed them to reduce the test burden. Not ideal for sure.