Build the simple-submit-rules plugin on its own stable-2.16 branch

The plugin's master branch is no longer compatible with core
gerrit on stable-2.16, and a stable-2.16 branch has been created
from the last compatible commit.

Change-Id: I51d2b7c270fb214f50b28338bc8d868d0ba4404b
diff --git a/jenkins/gerrit-bazel-plugin-simple-submit-rules.yaml b/jenkins/gerrit-bazel-plugin-simple-submit-rules.yaml
index 47b978c..479dd86 100644
--- a/jenkins/gerrit-bazel-plugin-simple-submit-rules.yaml
+++ b/jenkins/gerrit-bazel-plugin-simple-submit-rules.yaml
@@ -1,9 +1,7 @@
 - project:
     name: simple-submit-rules
     jobs:
-      - 'plugin-{name}-bazel-{branch}-{gerrit-branch}':
+      - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
-          gerrit-branch:
-            - master
             - stable-2.16