doc: add a note about Raft

This commit adds a note to specify
that the information on the Handling
Failures page only refers to clusters
with Raft enabled.
Also, the comment is included to remove
the note in future versions.

docs/troubleshooting/handling-node-failures.rst

@@ -1,6 +1,16 @@
 Handling Node Failures
 ------------------------
 
+.. note::
+
+    This page applies to ScyllaDB clusters that use Raft to ensure consistency. 
+    You can verify that Raft-based consistent management is enabled for your 
+    cluster in the ``scylla.yaml`` file (enabled by default): 
+    ``consistent_cluster_management: true``
+
+ .. REMOVE IN FUTURE VERSIONS - Remove the above note when Raft is mandatory
+    and default for both new and existing clusters.
+
 ScyllaDB relies on the Raft consensus algorithm, which requires at least a quorum 
 of nodes in a cluster to be available. If one or more nodes are down, but the quorum 
 is live, reads, writes, and schema updates proceed unaffected. When the node that