clang-tidy: add ending namespace comments

Found with google-readability-namespace-comments

Signed-off-by: Rosen Penev <[email protected]>

taglib/mpc/mpcproperties.cpp

@@ -201,7 +201,7 @@ namespace
   // This array looks weird, but the same as original MusePack code found at:
   // https://www.musepack.net/index.php?pg=src
   const unsigned short sftable [8] = { 44100, 48000, 37800, 32000, 0, 0, 0, 0 };
-}
+}  // namespace
 
 void MPC::Properties::readSV8(File *file, long streamLength)
 {