[llvm] Revert "[SLP]Support revectorization of the previously vectorized scalars" (PR #134604)

[Alexander Kornienko via llvm-commits]

alexfh wrote:

This breaks Transforms/SLPVectorizer/X86/reordered-masked-loads.ll. Apparently, the test relies on some changes in https://github.com/llvm/llvm-project/pull/133091. 

https://github.com/llvm/llvm-project/pull/134604