.gitlab-ci.yml: Trying to fix code quality reports

This hasnt been working for a while, it might be because GitLab
doesnt quite grasp that we have multiple branches to merge MRs to,
or it might be because they have change the API and broken back compat
in some way.

See: https://docs.gitlab.com/ee/ci/examples/code_quality.html
10 jobs for tristan/fix-code-quality in 39 minutes and 24 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Prepare
passed #92112873
source_dist

00:00:25

 
  Test
passed #92112879
docs

00:17:18

passed #92112874
tests-debian-9

00:34:01

passed #92112875
tests-fedora-27

00:33:39

passed #92112876
tests-fedora-28

00:34:38

passed #92112877
tests-ubuntu-18.04

00:33:19

passed #92112878
tests-unix

00:16:37

 
  Post
passed #92112881
analysis

00:00:40

passed #92112880
allowed to fail
code_quality

00:04:17

passed #92112882
coverage

00:00:32

85.59%