fix(animationFrame.spec): spec description fix

This test is not related to delay but the effect of unsubscribe on the resulting Subscription.

spec/schedulers/AnimationFrameScheduler-spec.ts

@@ -25,7 +25,7 @@ describe('Scheduler.animationFrame', () => {
     sandbox.restore();
   });
 
-  it('should cancel animationFrame actions when delay > 0', () => {
+  it('should cancel animationFrame actions when unsubscribed', () => {
     let actionHappened = false;
     const sandbox = sinon.sandbox.create();
     const fakeTimer = sandbox.useFakeTimers();