Hints for gnome-subtitles in main

Warnings

• asv-mimetypes-tag-deprecated
  org.gnome.GnomeSubtitles.appdata.xml:164 -
  The toplevel `mimetypes` tag is deprecated. Please use `mediatype` tags in a `provides` block instead to indicate that your software provides a media handler for the given types.
• translations-not-found
  Unable to add languages information, even though a translation tag was present in the MetaInfo file. Please check that its value is set correctly, and all locale files are placed in the right directories (e.g. /usr/share/locale/*/LC_MESSAGES/ for Gettext .mo files).
• screenshot-download-error
  Error while downloading screenshot from 'https://gnomesubtitles.org/files/screenshots/Screenshot-GnomeSubtitles-VideoTimesTranslation.png': URL was not found on the server.
  This might be a temporary server issue, or the screenshot is no longer available.