Explicitly indicate pull-request resource type
Explicitly indicate pull-request resource type

- additional_resource_types in the concourse manifest is not supported anymore:
  https://github.com/concourse/concourse/issues/521

cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,orange-cloudfoundry/buildpacks-ci,orange-cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,orange-cloudfoundry/buildpacks-ci