try to use container in gitlab registry

.gitlab-ci.yml

+image: gitlab.mn.tu-dresden.de:8000/s1140568/masterthesis:latest
+
 pdf:
   script:
       # use settings from .latexmkrc
@@ -13,5 +15,3 @@ pdf:
     paths:
     - "Felix-Hilsky-master-thesis.pdf"
     expire_in: 4 weeks
-  tags:
-    - shell