Fixed/added namespace ending comments using clang-tidy. NFC

The patch is generated using this command:

tools/clang/tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
  -checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
  llvm/lib/


Thanks to Eugene Kosov for the original patch!

llvm-svn: 240137

llvm/lib/ProfileData/CoverageMappingReader.cpp

@@ -315,7 +315,7 @@ struct SectionData {
     return std::error_code();
   }
 };
-}
+} // namespace
 
 template <typename T, support::endianness Endian>
 std::error_code readCoverageMappingData(