Link to deleting stale pipelines points to localhost:4000

[jhindulak]

Near the bottom of https://docs.armory.io/spinnaker/using_dinghy/#create-a-dinghyfile-from-an-existing-pipeline - there is a link to deleting a stale pipeline pointing to localhost:4000. It should be updated to https://docs.armory.io/spinnaker/using_dinghy/#deleting-stale-pipelines which resolves correctly.

Change required on L536.