Merge pull request #34842 from joshjms/post-etcd-govulncheck

etcd: Add post-etcd-govulncheck for release-3.4 branch

Author: k8s-ci-robot

config/jobs/etcd/etcd-postsubmits.yaml

@@ -67,6 +67,7 @@ postsubmits:
     branches:
     - main
     - release-3.6
+    - release-3.4
     decorate: true
     annotations:
       testgrid-dashboards: sig-etcd-postsubmits