Update troubleshooting-unbalanced-cluster.md (#2453)

Suggestion by Mirko Bez, cross linked from an internal docs issue.

It clarifies that the last operation of the troubleshooting doc requires
operator privileges, but maybe we want to explicitly mention that it's
not allowed in ECE, ECH or ECK deployments (not totally sure about it).

Author: eedugon

troubleshoot/elasticsearch/troubleshooting-unbalanced-cluster.md

@@ -80,3 +80,6 @@ $$$delete-desired-balance-request-example$$$
 DELETE /_internal/desired_balance
 ```
 
+::::{note}
+If your deployment runs on an orchestrating platform such as {{ech}}, {{ece}}, or {{eck}}, the desired balance can only be reset by a user with operator privileges. Refer to [operator privileges](/deploy-manage/users-roles/cluster-or-deployment-auth/operator-privileges.md) for more information.
+::::