change CI rust-fmt checks to stable rust

4 jobs for master in 23 minutes and 30 seconds (queued for 1 second)
Status Job ID Name Coverage
  Check
passed #204063
check

00:00:23

 
  Test
passed #204064
flatpak

00:15:59

 
  Deploy
passed #204065
pages

00:07:07

passed pages:deploy

00:00:01