Remove leftover clean:events rake task invocation (#46)

lib/graphql/anycable/tasks/clean_expired_subscriptions.rake

@@ -5,7 +5,7 @@ require "graphql-anycable"
 namespace :graphql do
   namespace :anycable do
     desc "Clean up stale graphql channels, subscriptions, and events from redis"
-    task clean: %i[clean:channels clean:subscriptions clean:events clean:fingerprint_subscriptions clean:topic_fingerprints]
+    task clean: %i[clean:channels clean:subscriptions clean:fingerprint_subscriptions clean:topic_fingerprints]
 
     namespace :clean do
       # Clean up old channels