[llvm] [CI] Update setup-python action to v5 for GHA (PR #95414)

[Jannick Kremer via llvm-commits]

DeinAlptraum wrote:

@boomanaiden154 @tstellar based on older PRs, I think you are the right people to review GHA stuff?

https://github.com/llvm/llvm-project/pull/95414