[DOCS] Clarify version compability in monitoring docs (#263)

Author: lcawl

docs/en/stack/monitoring/how-monitoring-works.asciidoc

@@ -29,8 +29,8 @@ differences between various subscription levels, see: https://www.elastic.co/sub
 IMPORTANT: In general, the monitoring cluster and the clusters being monitored
 should be running the same version of the stack. A monitoring cluster cannot
 monitor production clusters running newer versions of the stack. If necessary,
-the monitoring cluster can monitor production clusters running older versions,
-but the versions cannot differ by more than one major version.
+the monitoring cluster can monitor production clusters running the latest
+release of the previous major version.
 
 If you use {kib} to visualize data and administer the cluster, you might want to 
 create a dedicated {kib} instance for monitoring, rather than using a single