properties: add deprecation context to raft_replica_max_flush_delay_ms (#1305)

Author: paulohtb6

modules/upgrade/pages/deprecated/index.adoc

@@ -36,7 +36,7 @@ a| Client throughput quota cluster configuration:
 
 | 24.1.1
 | `raft_flush_timer_interval_ms`
-| Use xref:reference:cluster-properties.adoc#raft_replica_max_flush_delay_ms[`raft_replica_max_flush_delay_ms`] instead.
+| Use xref:reference:cluster-properties.adoc#raft_replica_max_flush_delay_ms[`raft_replica_max_flush_delay_ms`] instead. This configuration enforces a maximum delay since the last flush (timer-based flush), whereas the deprecated property controlled how often a partition checked for pending flush bytes. Because the semantics differ, review and adjust your values as needed.
 
 | 23.3.2
 | `space_management_enable_override`