remove unused image field

Author: razvan

tests/templates/kuttl/opa/40_superset.yaml.j2

@@ -20,7 +20,6 @@ metadata:
   name: superset
 spec:
   image:
-    custom: docker.stackable.tech/stackable/superset:4.0.2-stackable0.0.0-dev-opa
 {% if test_scenario['values']['superset'].find(",") > 0 %}
     custom: "{{ test_scenario['values']['superset'].split(',')[1] }}"
     productVersion: "{{ test_scenario['values']['superset'].split(',')[0] }}"