[llvm] [Reassociate] Drop weight reduction to fix issue 91417 (PR #91469)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

Still not completely clear to me what the original benefits of d7aeefebd6b049f017711cd7c6ef5f217a17b673 were meant to be, but the fix looks good to me. I confirm too the infinite loop of the original patch doesn't seem to come back.

https://github.com/llvm/llvm-project/pull/91469