Fix CI pipeline after GitLab upgrade

Fix the stage for the rebase check. After the upgrade it lloks like that the pipeline doesn't run any longer in the context of the forked project but in context of the master project such that the project path wasn't correct any longer. This allows now to compare upstream/master to HEAD.

approved this merge request

enabled an automatic merge when the pipeline for d90645f9 succeeds

canceled the automatic merge

added Simulation label

removed Simulation label

Dear @f.uhlig, @v.friese, @p.-a.loizeau,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

merged

mentioned in merge request !311 (closed)

changed milestone to %APR21