Update .gitlab-ci.yml file

.gitlab-ci.yml

@@ -34,7 +34,7 @@ trigger_cb_pipeline:
       --request POST 
       --form token=$CB_TRIGGER_TOKEN 
       --form ref=master 
-      --form "variables[WALBERLA_GITLAB_INSTANCE]=https://i10git.cs.fau.de" 
+      --form "variables[WALBERLA_GITLAB_INSTANCE]=https://$CI_SERVER_HOST" 
       --form "variables[WALBERLA_PROJECT_ID]=walberla/walberla" 
       --form "variables[WALBERLA_BRANCH]=master"
       "$CB_TRIGGER_API_URL"