Change note to warning

Get more attention from reader since we're recommending they stop
reading at this point.

docs/hooks/hook_civicrm_navigationMenu.md

@@ -15,7 +15,7 @@ This hook is called after the menus are rebuilt.
 
 You can use this hook to add new menu, add children to new menu and get the list of menu items for any parent.
 
-!!! note "Use the Civix implementation"
+!!! warning "Use the Civix implementation"
     [Civix](/extensions/civix.md) comes with helper functions `_EXTENSION_NAME_civix_insert_navigation_menu` and `_EXTENSION_NAME_civix_navigation_menu` that simplify the process of inserting menu items. Consider using these functions rather than using the examples below or writing your own implementation of this hook.
 
 ## Definition