docs(groups): add warning when local concurrency is set (#2762)

Author: roggervalf

docs/gitbook/bullmq-pro/groups/concurrency.md

@@ -19,4 +19,3 @@ const worker = new WorkerPro('myQueue', processFn, {
 ```
 
 The concurrency factor is global, so in the example above, independently of the concurrency factor per worker or the number of workers that you instantiate in your application, it will never process more than 3 jobs per group at any given time.
-

docs/gitbook/bullmq-pro/groups/local-group-concurrency.md

@@ -14,6 +14,10 @@ const groupId = 'my group';
 await queue.setGroupConcurrency(groupId, 4);
 ```
 
+{% hint style="warning" %}
+Make sure to also set the [Group Concurrency](concurrency.md) at the worker instance level along side with the desired local concurrency, as it is required for this feature to function properly and also will act as a default concurrency value for the groups that have no local concurrency defined.
+{% endhint %}
+
 And you can use the `getGroupConcurrency` method like this:
 
 ```typescript