clang-tidy: add ending namespace comments

Found with google-readability-namespace-comments

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

taglib/wavpack/wavpackfile.cpp

@@ -45,7 +45,7 @@ using namespace TagLib;
 namespace
 {
   enum { WavAPEIndex, WavID3v1Index };
-}
+} // namespace
 
 class WavPack::File::FilePrivate
 {

taglib/wavpack/wavpackfile.h

@@ -217,7 +217,7 @@ namespace TagLib {
       class FilePrivate;
       FilePrivate *d;
     };
-  }
-}
+  }  // namespace WavPack
+}  // namespace TagLib
 
 #endif

taglib/wavpack/wavpackproperties.h

@@ -143,7 +143,7 @@ namespace TagLib {
       class PropertiesPrivate;
       PropertiesPrivate *d;
     };
-  }
-}
+  }  // namespace WavPack
+}  // namespace TagLib
 
 #endif