Fix Debian.yml

Remove non-existing `backports` component:

    apt.cache.FetchFailedException:
    W:Failed to fetch http://ftp.debian.org/debian/dists/wheezy-backports/Release
    Unable to find expected entry 'backports/binary-amd64/Packages' in Release file (Wrong sources.list entry or malformed file),
    E:Some index files failed to download. They have been ignored, or old ones used instead.