docs(subscribe): update `subscribe` documentation (#5352)
docs(subscribe): update `subscribe` documentation (#5352)

* docs(subscribe): update `subscribe` documentation

* docs(subscribe): add comma after "In particular"

* docs(subscribe): add notice about asynchronously thrown errors

* docs(subscribe): add notice about deprecated usages of `subscribe` method (relates to #4159)

* docs(subscribe): add notice about using `subscribe` with no params

* docs(subscribe): fix example not to use deprecated `subscribe`

* docs(subscribe): add example with deprecated `subscribe` with notice that it's deprecated

* docs(subscribe): fix unsubscribe example replacing deprecated `subscribe` usage with Observer

* docs(subscribe): add notice that unprovided error handlers will cause throwing errors asynchronously

* docs(subscribe): fix return type

Closes #5339

* docs: minor grammar tweaks

And remove specific mention of deprecations. Let the signature
deprecations to the talking.

* docs: more minor tweaks

Co-authored-by: Nicholas Jamieson <3b9de09f2ff76afe9f0ad4fcae4ff68f52ec7fc4@cartant.com>
ReactiveX/rxjs,ReactiveX/RxJS,ReactiveX/rxjs,martinsik/rxjs,martinsik/rxjs,benlesh/RxJS,ReactiveX/RxJS,benlesh/RxJS,ReactiveX/rxjs,ReactiveX/RxJS,benlesh/RxJS,martinsik/rxjs,martinsik/rxjs,ReactiveX/rxjs,ReactiveX/RxJS,benlesh/RxJS