clang-tidy: add ending namespace comments

Found with google-readability-namespace-comments

Signed-off-by: Rosen Penev <rosenp@gmail.com>

taglib/wavpack/wavpackproperties.cpp

@@ -255,7 +255,7 @@ namespace
     return getMetaDataChunk(block, ID_DSD_BLOCK);
   }
 
-}
+}  // namespace
 
 void WavPack::Properties::read(File *file, long streamLength)
 {