[llvm] [LAA] strip unnecessary getUniqueCastUse (PR #92119)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Thanks for sanity-checking this: I previously didn't manage to cook up a sensible test. Now, the new tests are in #92253, and I've updated this patch to show the test update.

https://github.com/llvm/llvm-project/pull/92119