fix(aio): fix test message's mistake. (#21254)

duplicated message for 1st link. /heroes is 2nd link.

PR Close #21254

aio/content/examples/testing/src/app/app.component.spec.ts

@@ -130,7 +130,7 @@ function tests() {
   it('can get RouterLinks from template', () => {
     expect(links.length).toBe(3, 'should have 3 links');
     expect(links[0].linkParams).toBe('/dashboard', '1st link should go to Dashboard');
-    expect(links[1].linkParams).toBe('/heroes', '1st link should go to Heroes');
+    expect(links[1].linkParams).toBe('/heroes', '2nd link should go to Heroes');
   });
 
   it('can click Heroes link in template', () => {