Fix pubsub-light and sse-gateway plugin versions

The latest versions of these plugins are not compatible anymore with
Jenkins 2.60.3.

Change-Id: I7fcf1cedd7d86c4fe3a9ecd5351b3963f4e604c0
diff --git a/jenkins-docker/master/plugins.txt b/jenkins-docker/master/plugins.txt
index c7050f9..6089a46 100644
--- a/jenkins-docker/master/plugins.txt
+++ b/jenkins-docker/master/plugins.txt
@@ -69,8 +69,10 @@
 pipeline-stage-tags-metadata:1.2
 pipeline-stage-view:2.10
 plain-credentials:1.4
+pubsub-light:1.12
 scm-api:2.2.7
 script-security:1.44
+sse-gateway:1.19
 ssh-credentials:1.14
 ssh-slaves:1.26
 structs:1.14