[DOCS] added coming tags for `zen.discovery.publish_timeout` made dynamic

docs/reference/cluster/update-settings.asciidoc

@@ -146,7 +146,7 @@ All the disable allocation settings have been deprecated in favour for
 `discovery.zen.minimum_master_nodes`::
      See <<modules-discovery-zen>>
 
-`discovery.zen.publish_timeout`::
+`discovery.zen.publish_timeout` coming[1.1.0, The setting existed before but wasn't dynamic]::
      See <<modules-discovery-zen>>
 
 [float]

docs/reference/modules/discovery/zen.asciidoc

@@ -158,4 +158,5 @@ updates its own cluster state and replies to the master node, which waits for
 all nodes to respond, up to a timeout, before going ahead processing the next
 updates in the queue. The `discovery.zen.publish_timeout` is set by default
 to 30 seconds and can be changed dynamically through the
-<<cluster-update-settings,cluster update settings api>>.
+<<cluster-update-settings,cluster update settings api>> coming[1.1.0, The
+setting existed before but wasn't dynamic].