Update Dockerfile

Dockerfile

@@ -65,7 +65,7 @@ RUN apt-get update && apt-get install -y \
     && rm -rf /var/lib/apt/lists/* \
     service cron start
 # Execute all following commands as the papermc user
-FROM gitlab.cl.uni-heidelberg.de:5050/tmueller/UID-Handler:beta
+FROM tmueller/UID-Handler:beta
 
 # Start script and also entrypoint for the container
 CMD ["sh", "/papermc.sh"]