Revert "[SCEV] Don't walk uses of phis without SCEV expression when forgetting"

This reverts commit faf9f11589ce892b31d271917cf840f8ca903221.

Issues with this patch have been reported in
https://reviews.llvm.org/D100264#2689917 and
https://bugs.llvm.org/show_bug.cgi?id=49967.

GitOrigin-RevId: a1ed025d0ef99ba76c30b3d3753e5c2c40f9b755
2 files changed