delete upload-stemcell task as it is deprecated
delete upload-stemcell task as it is deprecated

* this was done independent of any story

Co-authored-by: Angela Chin <09c3fe443cd90255b3ab6945ab331bb5cdf11ccb@pivotal.io>

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