Add exception for OCPBUGS-86308

The details are in the bug.

Author: hongkailiu

test/extended/machines/scale.go

@@ -260,6 +260,8 @@ var _ = g.Describe("[sig-cluster-lifecycle][Feature:Machines][Serial] Managed cl
 				return "https://issues.redhat.com/browse/OCPBUGS-65896"
 			case "dns":
 				return "https://redhat.atlassian.net/browse/OCPBUGS-86009"
+			case "image-registry":
+				return "https://redhat.atlassian.net/browse/OCPBUGS-86308"
 			case "network":
 				return "https://redhat.atlassian.net/browse/OCPBUGS-85677"
 			default: