* update(scale-out): docs for redis backplane
The sticky session was a little bit vague so that one might think even if they use just WebSocket for all the clients and use Redis backplane they still might need "sticky sessions". There was a clarification by @davidfowl [here](https://twitter.com/davidfowl/status/1212068926676275202?s=20)
* Update scale.md
* Update scale.md
* Update scale.md
Co-authored-by: Rick Anderson <3605364+Rick-Anderson@users.noreply.github.com>