CI: update to 1.6.3 of the GitLab CI Template

wim leers → credited longwave → .

@bnjmnm reported Stylelint was breaking in recent CI runs, this should be fixed by 📌 Update Stylelint formatter for Stylelint 16 Active but we also need to complete this now.

The Stylelint job fails, but that fails already; this needs fixing over in 📌 Update Stylelint formatter for Stylelint 16 Active (see 📌 Fix CI for Stylelint 16 Active for a test of that fix)

We're updating to ref: $_GITLAB_TEMPLATES_REF (from ref: 1.5.x-latest), so currently that's already 1.6.10!

Manually started the following CI jobs in the last/current CI pipeline, because they are only triggered when relevant code is changed, and a change to the CI pipeline definition itself is not considered such a change at this time:

• composer-lint
• phpcs
• phpstan
• stylelint
• cypress E2E
• cypress unit

(I see @longwave did the same in the previous CI pipeline: https://git.drupalcode.org/project/experience_builder/-/pipelines/363693 — but better to be safe than sorry!)