It turned out, that pushing all warning to GitLab resulted in being too
noisy. There were more than 30 issues opened in no time, often
duplicates, due to how GitLab maps or rather doesn't map alerts in the
free version.

This reverts commit de6e02d9.

This patch enables the delivery of alerts with the severity warning to
GitLab, which allows to handle the issues without causing alert fatique.

The unstable main builds were used to the requirement for an unreleased
fix. This switches now back to a stable release in order to keep
stability long term.