clang-tidy: add ending namespace comments

Found with google-readability-namespace-comments

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

bindings/c/tag_c.cpp

@@ -69,7 +69,7 @@ namespace
   {
     return String(s, unicodeStrings ? String::UTF8 : String::Latin1);
   }
-}
+}  // namespace
 
 void taglib_set_strings_unicode(BOOL unicode)
 {