Remove WeekSubscribe extension method

[maxkoshevoi]

As discovered in #987 WeekSubscribe should never be used on week events. If it does, subscriber will get unsubscribed on first GC run.

And since this repository also includes ObservableObject that uses WeekEventManager, it makes WeekSubscribe obsolete. Both do the same thing, and if used at the same time, user will get issue descried above.

So, should it be removed, or should we add a check that subscriber cannot be ObservableObject?

CC: @pictos, @brminnick, @jfversluis

[pictos]

To me it's ok to remove it.

[brminnick]

Agreed