triage-policies: Add Regression

Initiality sounds like regressions should be together with
Bug, Feature or such, but in reality
it looks like something by itself, so take the label
as enough by being alone
3 jobs for master in 8 minutes (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #207907
flatpak devel

00:07:06

9.0%
 
  Deploy
passed #207908
pages

00:00:53

passed pages:deploy

00:00:00