Fix the diagnostic.cpp test to explicitly disable more google checks

Imagine, hypothetically, that you had a build of clang-tidy that enabled
the google-* checks by default.  If you had such a binary, then this
test would fail.  Making it pass in that configuration isn't such a bad
thing.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@213085 91177308-0d34-0410-b5e6-96231b3b80d8