Correct the menutype descriptions

PR for #16200

The description for the menu heading  and text sperator types are incorect

The heading is only for a parent eg Users and it cannot be used to seperate items within a menu. Thats what the text seperator is for

administrator/language/en-GB/en-GB.com_menus.ini

@@ -221,9 +221,9 @@ COM_MENUS_TYPE_CONTAINER_DESC="This will create a container menu which will show
 COM_MENUS_TYPE_EXTERNAL_URL="URL"
 COM_MENUS_TYPE_EXTERNAL_URL_DESC="An external or internal URL."
 COM_MENUS_TYPE_HEADING="Menu Heading"
-COM_MENUS_TYPE_HEADING_DESC="A heading for use within menus, useful when separating menus with a separator."
+COM_MENUS_TYPE_HEADING_DESC="A heading for the parent of submenu items."
 COM_MENUS_TYPE_SEPARATOR="Text Separator"
-COM_MENUS_TYPE_SEPARATOR_DESC="A text separator."
+COM_MENUS_TYPE_SEPARATOR_DESC="A text separator, useful to seperate items within a menu."
 COM_MENUS_TYPE_SYSTEM="System Links"
 COM_MENUS_TYPE_UNEXISTING="Component '%s' does not exist."
 COM_MENUS_TYPE_UNKNOWN="Unknown"