Raise minimal nbxmpp version

Runtime check already uses the new version.
3 jobs for updateReadme in 3 minutes and 23 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #15630
run-appdata

00:00:06

passed #15629
run-tests

00:03:05

 
  Build
passed #15631
run-build

00:00:11