Update /api/v4/cluster/status docs (#28189)

Co-authored-by: Mattermost Build <build@mattermost.com>

api/v4/source/cluster.yaml

@@ -4,8 +4,9 @@
         - cluster
       summary: Get cluster status
       description: >
-        Get a set of information for each node in the cluster, useful for
-        checking the status and health of each node.
+        Get a list of all healthy nodes, including local information and
+        status of each one. If a node is not present, it means it is not
+        healthy.
 
         ##### Permissions