chore(list): simplify next sibling end user navigation

nextSibling.click() takes care of:
- setting checked to true
- focusing nextSibling
- fire a change event

radio/lib/single-selection-controller.ts

@@ -215,14 +215,9 @@ export class SingleSelectionController implements ReactiveController {
         }
       }
 
-      // The next sibling should be checked and focused.
-      nextSibling.checked = true;
+      // The next sibling should be checked, focused and dispatch a change event
       nextSibling.removeAttribute('tabindex');
-      nextSibling.focus();
-      // Fire a change event since the change is triggered by a user action.
-      // This matches native <input type="radio"> behavior.
-      nextSibling.dispatchEvent(new Event('change', {bubbles: true}));
-
+      nextSibling.click();
       break;
     }
   };

radio/radio_test.ts

@@ -138,7 +138,7 @@ describe('<md-radio>', () => {
       expect(a2.element.checked).withContext('prev radio checked').toBeFalse();
     });
 
-    it('Using arrow right should fire a change event', async () => {
+    it('dispatched a change event on user navigation', async () => {
       const {harnesses, root} = await setupTest(radioGroupPreSelected);
       const changeHandler = jasmine.createSpy('changeHandler');
       root.addEventListener('change', changeHandler);
@@ -146,7 +146,7 @@ describe('<md-radio>', () => {
       expect(a2.element.checked)
           .withContext('default checked radio')
           .toBeTrue();
-      
+
       await simulateKeyDown(a2.element, 'ArrowRight');
 
       expect(changeHandler).toHaveBeenCalledTimes(1);