Build reviewers-by-blame plugin on stable-3.4 branch

Change-Id: I61a07e6babc1b1c9944b701fd278d9fe6393069f

jenkins/gerrit-bazel-plugin-reviewers-by-blame.yaml

diff --git a/jenkins/gerrit-bazel-plugin-reviewers-by-blame.yaml b/jenkins/gerrit-bazel-plugin-reviewers-by-blame.yaml
index 24f91a6..fe90119 100644
--- a/jenkins/gerrit-bazel-plugin-reviewers-by-blame.yaml
+++ b/jenkins/gerrit-bazel-plugin-reviewers-by-blame.yaml
@@ -9,6 +9,7 @@
             - master
           gerrit-branch:
             - master
+            - stable-3.4
             - stable-3.3
             - stable-3.2
             - stable-3.1