Stop displaying priority in the roster and vcard views

Priority is a remnant of the pre-carbons world, where it would be used
by the server of the recipient to choose which resource to route an
incoming message to, when addressed to the bare JID.

Nowadays carbons is widespread enough that it makes sense to stop
displaying this old bit of information.
3 jobs for dont-display-priority in 2 minutes and 49 seconds (queued for 1 second)