Remove unneeded legacy scope docker-worker:capability:privileged (mozilla#377)

Author: petemoore

.taskcluster.yml

@@ -85,8 +85,6 @@ tasks:
             expires: {$fromNow: '2 weeks'}
             path: /image.tar.zst
             type: file
-      scopes:
-        - docker-worker:capability:privileged
       metadata:
         name: TaskBoot docker build
         description: Taskcluster boot utilities - build latest docker image