[clangtidy] Remove old copy of ExprMutationAnalyzer
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