Change the contact address in the footer from debian-www to the contact page

Also remove the note asking translators to mention mails should be in English,
since the existing contact page already mentions that Debian uses English.

This will empower people to find a better contact for their enquiry
rather than defaulting to the debian-www mailing list and
having debian-www readers redirect them to the right place.

This will also reduce the amount of off-topic mail on debian-www
and mean that debian-www readers spend less time answering them.

Wording-by: Justin B Rye <justin.byam.rye@gmail.com>
Closes: https://bugs.debian.org/1009253