Drop instructions for manual port forwarding in Vagrant

Since vagrant's 4ff12aa080e50709a1d72054ab5fa60d4f05ac7e, the port
forward gets set up automatically when provisioning the wikimetrics
role. Hence, the manual setting up is no longer needed.

Change-Id: I57c7649c956201367ac2d4105754cfb6c1c7e169
Merge "Drop instructions for manual port forwarding in Vagrant"