[add] a note for fieldset show()/hide() methods

Author: mafanya23

docs/form/api/fieldset/fieldset_hide_method.md

@@ -8,6 +8,10 @@ description: You can explore the hide method of the Fieldset control of Form in
 
 @short: hides a Fieldset control
 
+:::info
+Note that the method calls the `hide()` methods of the nested controls.
+:::
+
 @signature: {'hide(): void;'}
 
 @example:

docs/form/api/fieldset/fieldset_show_method.md

@@ -8,10 +8,16 @@ description: You can explore the show method of the Fieldset control of Form in
 
 @short: shows a Fieldset control on the page
 
+:::info
+Note that the method calls the `show()` methods of the nested controls.
+:::
+
 @signature: {'show(): void;'}
 
 @example:
 form.getItem("fieldset").show();
 
 @descr:
 The method doesn't invoke the fieldset events. It invokes the events of the nested controls.
+
+