test(engine): fix flaky test

The test was flaky because it could occur that the messages got published before the subscription were opened.
As the messages have no TTL this means they were not getting correlated, as expected.

engine/src/test/java/io/camunda/zeebe/engine/processing/bpmn/subprocess/EmbeddedSubProcessTest.java

@@ -24,6 +24,7 @@
 import io.camunda.zeebe.protocol.record.ValueType;
 import io.camunda.zeebe.protocol.record.intent.JobIntent;
 import io.camunda.zeebe.protocol.record.intent.MessageIntent;
+import io.camunda.zeebe.protocol.record.intent.MessageSubscriptionIntent;
 import io.camunda.zeebe.protocol.record.intent.ProcessEventIntent;
 import io.camunda.zeebe.protocol.record.intent.ProcessInstanceIntent;
 import io.camunda.zeebe.protocol.record.intent.VariableIntent;
@@ -623,10 +624,15 @@ public void shouldNotTriggerBoundaryEventWhenFlowscopeIsInterrupted() {
             .withVariable("correlationKey", "correlationKey")
             .create();
 
-    RecordingExporter.processInstanceRecords(ProcessInstanceIntent.ELEMENT_ACTIVATED)
-        .withProcessInstanceKey(processInstanceKey)
-        .withElementId("task")
-        .await();
+    assertThat(
+            RecordingExporter.messageSubscriptionRecords(MessageSubscriptionIntent.CREATED)
+                .withProcessInstanceKey(processInstanceKey)
+                .limit(2))
+        .describedAs(
+            "The 2 message subscriptions must be created before we publish the "
+                + "messages. As the messages have a TTL of 0 seconds")
+        .describedAs("")
+        .hasSize(2);
 
     // when
     // We need to make sure no records are written in between the publish commands. This could