[RemoveRedundantDebugValues] Enable machine verification after this pass

Machine verification after RemoveRedundantDebugValues has been disabled
since the pass was first added in D105279, but I guess this was just due
to copy-and-paste. Enabling it does not show any problems in check-llvm
in an LLVM_ENABLE_EXPENSIVE_CHECKS build.

Differential Revision: https://reviews.llvm.org/D110688