Add missing VLAN tag in the example bess-upf config

Change-Id: I14524ab7886032fab23d873da6c93a099f13fd69
diff --git a/edge_deployment/bess_upf_deployment.rst b/edge_deployment/bess_upf_deployment.rst
index 89cb1eb..fb8e101 100644
--- a/edge_deployment/bess_upf_deployment.rst
+++ b/edge_deployment/bess_upf_deployment.rst
@@ -99,9 +99,11 @@
        access:
          ip: "192.168.3.1/24"
          gateway: "192.168.3.254"
+         vlan: 3
        core:
          ip: "192.168.4.1/24"
          gateway: "192.168.4.254"
+         vlan: 4
      # Below is required only when connecting to 5G core
      cfgFiles:
        upf.json: