Revert "Maybe add new warning for shadowing simple tag types"

This reverts commit 2b43f500cfea10a8c59c986dcfc24fd08eecc77d.

This was accidentally committed because I failed to notice my client
wasn't clean prior to submitting a fix for a crasher.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197410 91177308-0d34-0410-b5e6-96231b3b80d8