Use usageAlternatives with v2-clean

[philderbeast]

Fixes #12148.

---

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[ffaf1]

Should this be erased?

cabal/cabal-install/src/Distribution/Client/Setup.hs

Line 316 in 4907eec

, "new-clean"

[philderbeast]

Should this be erased?

I don't think so with such a narrow pull request. Perhaps we need an issue to remove the lot of them, if not already covered by #9109?

cabal/cabal-install/src/Distribution/Client/Setup.hs

Lines 304 to 318 in 4907eec

	, "new-build"
	, "new-configure"
	, "new-target"
	, "new-repl"
	, "new-freeze"
	, "new-run"
	, "new-test"
	, "new-bench"
	, "new-haddock"
	, "new-exec"
	, "new-update"
	, "new-install"
	, "new-clean"
	, "new-sdist"
	, "new-haddock-project"

[Mikolaj]

OH, these were the times!