Use Pulsar 3.3.4 in PulsarTestContainerSupport

This sets the image tag from `latest` to `3.3.4` in order
to ensure the default tag matches up w/ the version of
Pulsar supported by Spring for Apache Pulsar.

See #1014

Author: onobc

spring-pulsar-test/src/main/java/org/springframework/pulsar/test/support/PulsarTestContainerSupport.java

@@ -33,7 +33,7 @@ public interface PulsarTestContainerSupport {
 	PulsarContainer PULSAR_CONTAINER = new PulsarContainer(getPulsarImage());
 
 	static DockerImageName getPulsarImage() {
-		return DockerImageName.parse("apachepulsar/pulsar:latest");
+		return DockerImageName.parse("apachepulsar/pulsar:3.3.4");
 	}
 
 	@BeforeAll