remove aliases for deprecated pkg/pubsub

The aliases are included in the 22 release branch, so we can remove them
from master.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/pubsub/publisher.go

@@ -1,17 +0,0 @@
-package pubsub // import "github.com/docker/docker/pkg/pubsub"
-
-import "github.com/moby/pubsub"
-
-// NewPublisher creates a new pub/sub publisher to broadcast messages.
-// The duration is used as the send timeout as to not block the publisher publishing
-// messages to other clients if one client is slow or unresponsive.
-// The buffer is used when creating new channels for subscribers.
-//
-// Deprecated: use github.com/moby/pubsub.NewPublisher
-var NewPublisher = pubsub.NewPublisher
-
-// Publisher is basic pub/sub structure. Allows to send events and subscribe
-// to them. Can be safely used from multiple goroutines.
-//
-// Deprecated: use github.com/moby/pubsub.Publisher
-type Publisher = pubsub.Publisher