Add pubsub.in-memory to conformance test workflow (#1126)

Co-authored-by: Long Dai <long0dai@foxmail.com>
Co-authored-by: Artur Souza <artursouza.ms@outlook.com>

.github/workflows/conformance.yml

@@ -58,6 +58,7 @@ jobs:
         - pubsub.mqtt-vernemq
         - pubsub.hazelcast
         - pubsub.rabbitmq
+        - pubsub.in-memory
         - secretstores.kubernetes
         - secretstores.localenv
         - secretstores.localfile