Build go-import plugin for stable-3.13 and stable-3.14

Add the missing Gerrit stable branches to the go-import plugin build
matrix.

Change-Id: Icb45b90dc8ff5370d8c788948012e8512efc4569

jenkins/gerrit-bazel-plugin-go-import.yaml

diff --git a/jenkins/gerrit-bazel-plugin-go-import.yaml b/jenkins/gerrit-bazel-plugin-go-import.yaml
index 964855f..1e31dcc 100644
--- a/jenkins/gerrit-bazel-plugin-go-import.yaml
+++ b/jenkins/gerrit-bazel-plugin-go-import.yaml
@@ -7,4 +7,6 @@
           gerrit-branch:
             - stable-3.11
             - stable-3.12
+            - stable-3.13
+            - stable-3.14
             - master