[Ref-Guide] Wrong documentation for solrcloud-autoscaling-overview.doc

In my understanding, since version 7.1 and the creation of Triggers and TriggerActions, the bold text below in not necessary since management operations will be invoked automatically. There is no patch to submit. The text has just to be removed.

Cluster management operations are currently invoked manually. In the future, these cluster management operations may be invoked automatically in response to cluster events such as a node being added or lost (link).