For new tarballs, send mail to a new non mailing list alias (Infrastructure#954)

deprecate util.py, unused and ancient.

Now that commits-list is gone, deprecate gnome-post-receive-email, webhooks (and/or hookshot) should be used instead

This reverts commit 9a2ed7b6.

1. commits-list being retired (activity + feed can be used as a replacement)
2. no need to generate a local filesystem doap file copy anymore
3. no need to generate a list of repo committers, gitlab already handles
   that these days