SchemaRegistrySerializationSpec: flaky test

container startup: ``` [info] SchemaRegistrySerializationSpec: [info] docs.scaladsl.SchemaRegistrySerializationSpec *** ABORTED *** (1 minute) [info] java.lang.RuntimeException: java.util.concurrent.ExecutionException: org.testcontainers.containers.ContainerLaunchException: Container startup failed for image confluentinc/cp-kafka:7.9.0 ```