TF: remove subnet0_id
TF: remove subnet0_id

This has moved to paas-bootstrap now and is used for concourse deployment.

alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf