providers: jabber.fr: update properties

Folowing an update of our prosody modules and config, we now have the following HTTP upload limits:

• 100 MB max/file (up from 10)
• 200 MB/user/day (down from unlimited)
• 14 days of file retention (down from unlimited) This has been reflected in the wiki page linked as a truth source.

I can also add that our bus factor is currently two, but there is no online statement reflecting that yet.

Also registration is now enabled again, it was accidentally disabled during the maintenance two days ago.