EKS clusters implement `LoadBalancer` type services with ELBs; when an
EKS cluster is destroyed via terraform these ELBs are not automatically
deleted. The continued presence of these ELBs will remain attached to
the associated subnets and prevent the subnets and VPC from being
destroyed.
This commit resolves the issue by explicitly deleting the `gitpod`
namespace (and pausing to allow the ELBs to be removed) before
continuing.