Update gitlab-ci.yml to match latest version provided by Salsa-CI project

See https://salsa.debian.org/salsa-ci-team/dummypackage/tree/master/debian
6 jobs for master in 5 minutes and 41 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #191681
build

00:02:28

 
  Test
passed #191684
autopkgtest

00:03:11

passed #191685
blhc

00:01:20

passed #191683
lintian

00:02:02

passed #191686
piuparts

00:02:56

passed #191682
reprotest

00:02:36