[DOCS] Add X-Pack upgrade details (#29038)

docs/reference/upgrade/cluster_restart.asciidoc

@@ -26,6 +26,9 @@ recovery.
 include::synced-flush.asciidoc[]
 --
 
+. *Stop any machine learning jobs that are running.* See
+{xpack-ref}/stopping-ml.html[Stopping Machine Learning].
+
 . *Shutdown all nodes.*
 +
 --
@@ -124,3 +127,5 @@ GET _cat/recovery
 --------------------------------------------------
 // CONSOLE
 --
+
+. *Restart machine learning jobs.* 

docs/reference/upgrade/rolling_upgrade.asciidoc

@@ -32,6 +32,9 @@ include::synced-flush.asciidoc[]
 
 --
 
+. *Stop any machine learning jobs that are running.* See
+{xpack-ref}/stopping-ml.html[Stopping Machine Learning].
+
 . [[upgrade-node]] *Shut down a single node*.
 +
 --
@@ -147,6 +150,8 @@ for each node that needs to be updated.
 
 --
 
+. *Restart machine learning jobs.* 
+
 [IMPORTANT]
 ====================================================