Build ghs-upload-pack-metrics against all maintained versions

Build ghs-upload-pack-metrics also against gerrit 3.11 and gerrit 3.12.

Change-Id: I0afb1228fe4b088a0904031c4a95e150f3533483
diff --git a/jenkins/gerrit-bazel-plugin-ghs-metrics-collector.yaml b/jenkins/gerrit-bazel-plugin-ghs-metrics-collector.yaml
index 639635c..29e2943 100644
--- a/jenkins/gerrit-bazel-plugin-ghs-metrics-collector.yaml
+++ b/jenkins/gerrit-bazel-plugin-ghs-metrics-collector.yaml
@@ -11,4 +11,6 @@
           branch:
             - master
           gerrit-branch:
+            - stable-3.12
+            - stable-3.11
             - stable-3.10