Revert "[clang] Introduce diagnostics suppression mappings (#112517)"
This reverts commit 12e3ed8de8c6063b15916b3faf67c8c9cd17df1f.
This reverts commit 41e3919ded78d8870f7c95e9181c7f7e29aa3cc4.
There are some buildbot breakages in
https://lab.llvm.org/buildbot/#/builders/18/builds/6832.