gitlab-ci: Use the prebuilt pipeline
this lowers maintenane and gives us lintian and autopktests for free (which will be useful to spot problems in !248 (merged)) early.
This needs !370 (merged)
this lowers maintenane and gives us lintian and autopktests for free (which will be useful to spot problems in !248 (merged)) early.
This needs !370 (merged)