Build project-group-structure for stable-3.10 on master

Change-Id: I4f5a58ada6cc19bc5b394314cf65b8935ea52e25
diff --git a/jenkins/gerrit-bazel-plugin-project-group-structure.yaml b/jenkins/gerrit-bazel-plugin-project-group-structure.yaml
index bf19eaa..c6e53e4 100644
--- a/jenkins/gerrit-bazel-plugin-project-group-structure.yaml
+++ b/jenkins/gerrit-bazel-plugin-project-group-structure.yaml
@@ -5,3 +5,4 @@
           branch:
             - master
           gerrit-branch:
+            - stable-3.10