Add gerrit-bsl-license as extra-gh-repo for the github plugin

Change-Id: I816a783ddca593f4f4f01c565458ff9a5f850f88

jenkins/gerrit-bazel-plugin-github.yaml

diff --git a/jenkins/gerrit-bazel-plugin-github.yaml b/jenkins/gerrit-bazel-plugin-github.yaml
index cd434ff..bf5a165 100644
--- a/jenkins/gerrit-bazel-plugin-github.yaml
+++ b/jenkins/gerrit-bazel-plugin-github.yaml
@@ -5,9 +5,12 @@
     jobs:
       - 'plugin-{name}-gh-bazel-{branch}':
           branch:
+            - stable-3.13
+      - 'plugin-{name}-gh-bazel-{branch}':
+          extra-gh-repos: 'gerrit-bsl-license'
+          branch:
             - master
             - stable-3.14
-            - stable-3.13
           extra-artifacts: >
             bazel-bin/plugins/github/github-*.jar,
             bazel-bin/plugins/github/github-*.jar-version