[clang] [flang] [llvm] Revert "Introduce -fexperimental-loop-fuse to clang and flang (#142686)" (PR #158764)

[Ryotaro Kasuga via llvm-commits]

https://github.com/kasuga-fj approved this pull request.

(As for one of the reviewers of PR #142686) LGTM, thanks!

https://github.com/llvm/llvm-project/pull/158764