appdata: Ensure up-to-date release version
It's easy to forget to add a new tag to the metainfo when doing a new release.
Address this with an additional test if appstream-util is recent enough to include the new validate-version command.
It's easy to forget to add a new tag to the metainfo when doing a new release.
Address this with an additional test if appstream-util is recent enough to include the new validate-version command.