Revert MSYS2 workaround once the issue is fixed upstream

[mati865]

Background:
Pacman from the archive installed by chocolatey is too old to properly unpack msys2-runtime which has been accidentally compressed with zstd too soon.
As the result Windows CI jobs started failing: https://dev.azure.com/rust-lang/rust/_build/results?buildId=29511&view=logs&j=90f6024d-9735-531d-4933-8983ca347d60

#72332 and #72384 have been created as temporary workaround. Once upstream resolves the issue they should be reverted.