Add admomition regarding core number change

Author: kbatuigas

modules/manage/pages/cluster-maintenance/cluster-balancing.adoc

@@ -133,6 +133,8 @@ Prior to Redpanda version 24.2, this meant that some cores on a broker could ina
 
 Starting in v24.2, topic-aware intra-broker partition balancing allows for dynamically reassigning partitions within a broker.  Redpanda prioritizes an even distribution of a topic's partition replicas across all cores in a broker. If a broker's core count changes, when the broker starts back up, Redpanda can check partition assignments across the broker's cores and reassign partitions, so that a balanced assignment is maintained across all cores. Redpanda can also check partition assignments when partitions are added to or removed from a broker, and rebalance the remaining partitions between cores.
 
+NOTE: Changing the number of CPU cores in a running cluster is supported from v24.2 only, and requires that you enable `node_local_core_assignment` as described in the previous note.
+
 To determine when to use intra-broker partition balancing, use the public metrics for CPU usage described in the xref:manage:monitoring.adoc#cpu-usage[Monitoring] guide.
 
 Configure the following properties to trigger intra-broker partition balancing: