[llvm] [LV] Strip redundant casts (NFC) (PR #128177)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for cleaning this up! It would be great if there was an automatic way to catch such redundant casts. I originally thought that maybe `cast` could have a `static_assert` to check if the source and destination types are the same, but I think there are a number of cases where they are redundant due to being used in some other templates :( 

https://github.com/llvm/llvm-project/pull/128177