Build imagare and reviewassistant plugins on stable-2.13

Change-Id: If5472b70003869ee2e6bfe7287772216f1bc3b31
diff --git a/jenkins/gerrit-buck-bazel-plugin-imagare.yaml b/jenkins/gerrit-buck-bazel-plugin-imagare.yaml
index ad83316..8e941a0 100644
--- a/jenkins/gerrit-buck-bazel-plugin-imagare.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-imagare.yaml
@@ -3,6 +3,7 @@
     jobs:
       - 'plugin-{name}-{branch}':
           branch:
+            - stable-2.13
             - stable-2.12
             - stable-2.11
       - 'plugin-{name}-bazel-{branch}':
diff --git a/jenkins/gerrit-buck-bazel-plugin-reviewassistant.yaml b/jenkins/gerrit-buck-bazel-plugin-reviewassistant.yaml
index bebb385..9186544 100644
--- a/jenkins/gerrit-buck-bazel-plugin-reviewassistant.yaml
+++ b/jenkins/gerrit-buck-bazel-plugin-reviewassistant.yaml
@@ -3,6 +3,7 @@
     jobs:
       - 'plugin-{name}-{branch}':
           branch:
+            - stable-2.13
             - stable-2.12
             - stable-2.11
       - 'plugin-{name}-bazel-{branch}':