[CI] Trigger rebuilds of the docker images in all applicable pacxx repositories

• https://gitlab.dune-project.org/joe/pacxx-docker
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-runtime
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-samples
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-llvm2
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-rv2
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-clang (pacxx-clang!2)

Replaces: #22 (closed)