[clangtidy] Remove old copy of ExprMutationAnalyzer

Summary:
This is 2/2 of moving ExprMutationAnalyzer from clangtidy to clang/Analysis.
ExprMutationAnalyzer is moved to clang/Analysis in D51948.
This diff migrates existing usages within clangtidy to point to the new
location and remove the old copy of ExprMutationAnalyzer.

Reviewers: george.karpenkov, JonasToth

Reviewed By: george.karpenkov

Subscribers: mgorny, a.sidorin, Szelethus, cfe-commits

Differential Revision: https://reviews.llvm.org/D51950

llvm-svn: 342006