Change back to upstream repo for fail2ban

Debian buster is now supported in their latest git release, so
no need to use the alternate upstream anymore
2 jobs for master in 9 minutes and 56 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #5260
librarian

00:08:35

 
  Deploy
passed #5261
deploy

00:01:20