examples: fix typos

Author: nacho

examples/custom_orientable/custom_orientable/imp.rs

@@ -62,7 +62,7 @@ impl ObjectImpl for CustomOrientable {
     }
 
     fn dispose(&self) {
-        // Child widgets need to be manually unparented in `dispose()`.
+        // Child widgets need to be manually parentless in `dispose()`.
         if let Some(child) = self.first_label.borrow_mut().take() {
             child.unparent();
         }

examples/custom_widget/ex_button/imp.rs

@@ -66,7 +66,7 @@ impl ObjectImpl for ExButton {
     }
 
     fn dispose(&self) {
-        // Child widgets need to be manually unparented in `dispose()`.
+        // Child widgets need to be manually parentless in `dispose()`.
         if let Some(child) = self.child.borrow_mut().take() {
             child.unparent();
         }