[llvm] [IR] Allow type change in ValueAsMetadata::handleRAUW (PR #76969)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse approved this pull request.

> I'll add a test case, but it'll only exercise usage rather then giving a true motivation.

IMO this is fine, it discourages people from breaking behaviours that you're relying on. LGTM.

https://github.com/llvm/llvm-project/pull/76969