fix: queue length in account event hook (#369)

lib/tasks/enqueue.js

@@ -296,7 +296,7 @@ class TaskEnqueue extends Task {
         cs.performQueueWebhook({
           event: 'leave',
           queue: this.data.name,
-          length: Math.max(members - 1, 0),
+          length: Math.max(members, 0),
           leaveReason: 'dequeued',
           leaveTime: Date.now(),
           dequeuer: opts.dequeuer