Hints for rhythmbox-plugin-alternative-toolbar in main

Hints

• metainfo-validation-hint
  Validation of the metainfo file yielded the following hint: The component ID [org.gnome.rhythmbox.rhythmbox-alternative-toolbar.addon] contains a hyphen/minus. Using a hyphen is strongly discouraged, to keep interoperability with other tools such as D-Bus. Ideally, replace any hyphens with an underscore ('_')