Add note about overridden broker images in che.properties

Add a small note to the plugin broker images config lines in
che.properties to make it clear that the Che Operator overrides the
properties by default.

Signed-off-by: Angel Misevski <amisevsk@redhat.com>

assembly/assembly-wsmaster-war/src/main/webapp/WEB-INF/classes/che/che.properties

@@ -543,6 +543,9 @@ che.singleport.wildcard_domain.ipless=false
 
 # Docker image of Che plugin broker app that resolves workspace tooling configuration and copies
 # plugins dependencies to a workspace
+#
+# Note these images are overridden by the Che Operator by default; changing the images here will not
+# have an effect if Che is installed via Operator.
 che.workspace.plugin_broker.metadata.image=quay.io/eclipse/che-plugin-metadata-broker:v3.4.0
 che.workspace.plugin_broker.artifacts.image=quay.io/eclipse/che-plugin-artifacts-broker:v3.4.0