Add test runner multiplier to account for slow CI runners

Per Infrastructure/Infrastructure#97, gcc150.osuosl.org uses platter
drives and so tests like ImapDB's that touch the disk are sloooooow.
5 jobs for wip/remove-ci-test-workaround in 40 minutes and 5 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build
passed #267531
fedora

00:18:29

passed #267532
ubuntu

00:24:26

 
  Test
passed #267533
flatpak

00:14:20

 
  Deploy
passed #267534
review

00:00:34

passed #267535
allowed to fail manual
stop_review

00:00:43