clang-tidy: [misc-use-override] Slightly tweak the wording of warning.

'final' should really be used with care.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@213501 91177308-0d34-0410-b5e6-96231b3b80d8
Merge remote-tracking branch 'origin/master'