Add missing upload_targets field

X-DeepSpeech: NOBUILD

taskcluster/simple-task.tyml

@@ -26,6 +26,7 @@ then:
     { $eval: build.routes }
 
   payload:
+    upload_targets: { $eval: build.upload_targets }
     artifacts_deps:
       python:
         $map: { $eval: build.artifacts_deps.python }