clang-tidy: add ending namespace comments

Found with google-readability-namespace-comments

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

taglib/audioproperties.h

@@ -122,6 +122,6 @@ namespace TagLib {
     AudioPropertiesPrivate *d;
   };
 
-}
+}  // namespace TagLib
 
 #endif