Hints for gromit-mpx in main

Hints

• asv-cid-contains-hyphen
  net.christianbeier.Gromit-MPX.appdata.xml:4 - net.christianbeier.Gromit-MPX
  The component ID contains a hyphen/minus. Using a hyphen is strongly discouraged, to improve interoperability with other tools such as D-Bus. A good option is to replace any hyphens with underscores (`_`).
• asv-content-rating-missing
  net.christianbeier.Gromit-MPX.appdata.xml -
  This component has no `content_rating` tag to provide age rating information. You can generate the tag data online by answering a few questions at https://hughsie.github.io/oars/