Do not recommend sleep at all around browser

On https://grafana.com/docs/k6/latest/using-k6-browser/recommended-practices/simulate-user-input-delay/ we do warn users about using sleep, but IMO it should just be a warning to *NOT* use it at all.

There is no reason to do it, and it will lead to problems as it blocks all execution

Start with the documented page at https://grafana.com/docs/k6/latest/using-k6-browser/recommended-practices/simulate-user-input-delay/. Locate the guidance about using sleep around browser interactions and revise it to warn users not to use sleep at all; done means the page clearly communicates that recommendation.

Written by the indexing model from the issue text.