d/salsa-ci.yml: Enable contrib and non-free apt components

Now that the pipeline can deal with this (salsa-ci-team/pipeline#55),
we can re-enable piuparts.

Gbp-Dch: ignore
6 jobs for master in 18 minutes and 32 seconds (queued for 3 seconds)
latest
Status Job ID Name Coverage
  Build
passed #203702
build

00:04:38

 
  Test
passed #203705
autopkgtest

00:04:07

passed #203706
blhc

00:01:29

passed #203704
lintian

00:02:03

passed #203707
piuparts

00:13:52

passed #203703
reprotest

00:05:33