Merge branch 'leipert-default-image-node-12' into 'master'

Update default CI image to use node@12

See merge request gitlab-org/gitlab-ce!29703

.gitlab-ci.yml

-image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.6.3-golang-1.11-git-2.21-chrome-73.0-node-10.x-yarn-1.12-postgresql-9.6-graphicsmagick-1.3.29"
+image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.6.3-golang-1.11-git-2.21-chrome-73.0-node-12.x-yarn-1.16-postgresql-9.6-graphicsmagick-1.3.29"
 variables:
   MYSQL_ALLOW_EMPTY_PASSWORD: "1"