[clang] [clang-format][NFC] Clean up FormatTestComments.cpp (PR #166029)

[Björn Schäpers via cfe-commits]

https://github.com/HazardyKnusperkeks approved this pull request.

Just out of curiosity, with which tool did you check for the duplicated strings?

https://github.com/llvm/llvm-project/pull/166029