Add test job for stable-3.9

Also remove the older branches that were previously removed from
project.yaml.

Change-Id: Id1689890d1839c0cb0537533a86525560f80080e
diff --git a/zuul.d/project.yaml b/zuul.d/project.yaml
index 3fa6e13..b172dad 100644
--- a/zuul.d/project.yaml
+++ b/zuul.d/project.yaml
@@ -9,5 +9,6 @@
         - test-gerrit-build-stable-3.6
         - test-gerrit-build-stable-3.7
         - test-gerrit-build-stable-3.8
+        - test-gerrit-build-stable-3.9
         - test-gitiles-build-master
         - test-install-build-essential
diff --git a/zuul.d/test-jobs.yaml b/zuul.d/test-jobs.yaml
index 0d527e9..4b69d1f 100644
--- a/zuul.d/test-jobs.yaml
+++ b/zuul.d/test-jobs.yaml
@@ -66,16 +66,6 @@
 
 # TODO remove unsupported stable gerrit builds.
 - job:
-    name: test-gerrit-build-stable-3.3
-    parent: test-gerrit-build-master
-    override-checkout: stable-3.3
-
-- job:
-    name: test-gerrit-build-stable-3.4
-    parent: test-gerrit-build-master
-    override-checkout: stable-3.4
-
-- job:
     name: test-gerrit-build-stable-3.5
     parent: test-gerrit-build-master
     override-checkout: stable-3.5
@@ -96,6 +86,11 @@
     override-checkout: stable-3.8
 
 - job:
+    name: test-gerrit-build-stable-3.9
+    parent: test-gerrit-build-master
+    override-checkout: stable-3.9
+
+- job:
     name: test-gitiles-build-master
     parent: gitiles-build
     files: