Docs: comments on router supervision are out of date

[Aaronontheweb]

Please describe what you are trying to understand

https://getakka.net/articles/actors/routers.html#supervision

"By default, pool routers use a custom strategy that only returns Escalate for all exceptions, the router supervising the failing worker will then escalate to its own parent"

Not true any more, as of #6295 in v1.4.50.

What did these pages not make clear?

Information is wrong - we use the default supervision strategy now and the documents should say so.

How can we do it better?

We just need to change this section to suggest that Pool routers now use Directive.Restart by default, like every other actor.

[Aaronontheweb]

Need to also clarify how to set the supervision strategy properly on routers:

So, is it also normal that overriding SupervisionStrategy the usual way is not having effect (e.g. breakpoint is not hit), as this must be done with Router.WithSupervisionStrategy?

We need a DocFx code reference for this type of stuff.