remove debianism file-content verification

remove debianism file-content verification

The code requires every index file we download to have a Package field,
but that doesn't hold true for all index we might want to download in
the future. Some might not even be deb822 formatted files…

The check was needed as apt used to accept unverifiable files like
Translation-*, but nowadays it requires hashes for these as well. Even
for unsigned repositories we interpret the Release file as binding now,
which means this check isn't triggerable expect for repositories which
do not have a Release file at all – something which is highly discouraged!

Git-Dch: Ignore