ci: remove unused script_helpers.sh
ci: remove unused script_helpers.sh

* the one true script_helpers.sh lives [here](https://github.com/cloudfoundry/networking-oss-deployments/blob/master/scripts/script_helpers.sh)

cloudfoundry-incubator/cf-routing-release,cloudfoundry-incubator/cf-routing-release,cloudfoundry-incubator/cf-routing-release