test: replace bitnami/cassandra imgage with cassandra (#3000)

Author: pichlermarc

.github/workflows/unit-test.yml

@@ -125,7 +125,7 @@ jobs:
           --health-timeout 5s
           --health-retries 5
       cassandra:
-        image: bitnami/cassandra:3
+        image: cassandra:3
         ports:
         - 9042:9042
       rabbitmq: