[llvm] [InstCombine] Drop range metadata when simplifying `fshl` with demanded bits (PR #173864)

[Yunbo Ni via llvm-commits]

cardigan1008 wrote:

> This doesn't have anything to do with vectors. `!range` is just an outdated, non-canonical way to spell `range(...)` here.
> 
> I think it makes sense to drop it in the interest of being conservative, but this should be done by using dropPoisonGeneratingAnnotations(), which covers both the attribute and the metadata.

Fixed. Also adjusted the description. Thanks. 

https://github.com/llvm/llvm-project/pull/173864