[clang] [llvm] Revert "Enable unnecessary-virtual-specifier by default" (PR #134105)

[Devon Loehr via cfe-commits]

DKLoehr wrote:

Thanks for the revert, can you link to a failed build or something so I know what exactly went wrong? Was the issue the presence of an unrecognized warning flag in the build files?

https://github.com/llvm/llvm-project/pull/134105