Remove unneeded destory definition
Remove unneeded destory definition

This was made redundant in the
[Use the same logic to destroy environment](https://github.com/alphagov/multicloud-deploy/commit/fc8ada0d28f8244ccc0a82dc851e03448648b55e) commit

alphagov/multicloud-deploy,alphagov/multicloud-deploy,alphagov/multicloud-deploy