pin hydra to v1.8 in pipeline

.gitlab-ci.yml

@@ -70,7 +70,7 @@ frontend-e2etest:
       alias: login
     - name: open.greenhost.net:4567/openappstack/single-sign-on/consent_provider:master
       alias: consent
-    - name: oryd/hydra:latest
+    - name: docker.io/oryd/hydra:v1.8
       alias: hydra
       command:
         - serve