Clearer language around upgrade sequence (#47422)

Author: robin13

docs/reference/upgrade/rolling_upgrade.asciidoc

@@ -7,11 +7,11 @@ a time so upgrading does not interrupt service. Running multiple versions of
 not supported, as shards cannot be replicated from upgraded nodes to nodes
 running the older version.
 
-It is best to upgrade the master-ineligible nodes in your cluster first and then
-upgrade the master-eligible nodes. Once enough of the master-eligible nodes have
-been upgraded they may form a cluster that nodes of older versions cannot join.
-If you upgrade the master-eligible nodes last then all the other nodes will not
-be running an older version and so they will be able to join the cluster.
+It is best to upgrade the master-eligible nodes in your cluster after all of
+the other nodes. Once you have started to upgrade the master-eligible nodes
+they may form a cluster that nodes of older versions cannot join. If you
+upgrade the master-eligible nodes last then all the other nodes will not be
+running an older version and so they will be able to join the cluster.
 
 Rolling upgrades are supported: