[llvm] Revert "[GitHub] Fix slow sccache install on macOS by upgrading macOS version (#77165)" (PR #77270)

[Craig Hesling via llvm-commits]

linux4life798 wrote:

@tstellar, any chance you could review and merge if approved?

This is just a revert of https://github.com/llvm/llvm-project/pull/77165.
I would rather revert first to ensure no one encounter the new cache issue and then work on the fix.

https://github.com/llvm/llvm-project/pull/77270