Remove appengine.IsCapabilityDisabled.
Remove appengine.IsCapabilityDisabled.

Change-Id: I39918199e71e92b46da1487ebf50647ee23f1a76

fuchsia-mirror/third_party-github.com-golang-appengine,flowlo/appengine,skyeunknown084/appengine,skyeunknown084/appengine,mzimmerman/appengine,golang/appengine,fuchsia-mirror/third_party-github.com-golang-appengine,mzimmerman/appengine,mzimmerman/appengine,golang/appengine,flowlo/appengine,flowlo/appengine,skyeunknown084/appengine