fix falling test app.component.spec.ts `should render title`

[ntedgi]

change lines

from:

   expect(compiled.querySelector('.content span').textContent).toContain(
      'playground app is running!'
    );

to:

  expect(compiled.querySelector('.github-fork-ribbon').textContent).toContain(
      'Fork me on GitHub'
    );

[4nxi0uss]

Hi, I'd like to try this!