contrib: Update recently-simplified code sample

Author: claremacrae

contributing/Testing/Example Tests.md

@@ -25,10 +25,8 @@ it('allows signifier emojis as part of the description', () => {
     expect(task).not.toBeNull();
     expect(task!.description).toEqual('this is a ✅ done task');
     expect(task!.status).toStrictEqual(Status.DONE);
-    expect(task!.dueDate).not.toBeNull();
-    expect(task!.dueDate!.isSame(moment('2021-09-12', 'YYYY-MM-DD'))).toStrictEqual(true);
-    expect(task!.doneDate).not.toBeNull();
-    expect(task!.doneDate!.isSame(moment('2021-06-20', 'YYYY-MM-DD'))).toStrictEqual(true);
+    expect(task!.dueDate).toEqualMoment(moment('2021-09-12'));
+    expect(task!.doneDate).toEqualMoment(moment('2021-06-20'));
 });
 ```
 <!-- endSnippet -->