Revert ".gitlab-ci.yml: remove nightly-$(date) again"

This reverts commit 50ac95f5.

Closes #113 (closed)

assigned to @wdconinc

enabled an automatic merge when the pipeline for 900c7ca1 succeeds

aborted the automatic merge because target branch was updated

added 2 commits

• 151137f9 - 1 commit from branch master
• c9b6987f - Revert ".gitlab-ci.yml: remove nightly-$(date) again"

Compare with previous version

enabled an automatic merge when the pipeline for c9b6987f succeeds

merged