[llvm] [IR] Simplify HasCachedHash with is_detected (NFC) (PR #159510)

[Jordan Rupprecht via llvm-commits]

rupprecht wrote:

> Does anyone else see this?

Also see it on the bazel buildbots, which bisects to this change: https://buildkite.com/llvm-project/upstream-bazel/builds/151045

https://github.com/llvm/llvm-project/pull/159510