fix(runtime-core): make watchEffect ignore deep option

[jiangying000]

Make watchEffect behavior not affected by deep option when the callback function returns a nested Reactive or Ref.

[jods4]

Why not fix the typings?

If watchEffect is a separate api (btw... why?) then deep makes no sense, so remove it from options?

What also makes no sense to me is returning a value from watchEffect callback. It's just discarded right? If you want to cache a result then the api would be computed.

EDIT: Forget that, I just noticed that the test is for JS users and actively disabled typing. 😴