Specify that Effects run on commit, not render

[eps1lon]

preview: useEffect reference docs

I had two instances recently where people were confused by useEffect not running after each render (https://github.com/facebook/react/issues/35221 and https://github.com/facebook/react/issues/34730). I think the docs aren't super clear about this and you need a bit of a React brain to infer the actual behavior.

In the learn section where we introduce the render and commit phase, we don't talk about Effects: https://react.dev/learn/render-and-commit. That seems fine to me since Effects are an advanced concept.

However, the useEffect reference docs, say that the setup runs after "render" not after "commit": https://react.dev/reference/react/useEffect#parameters

I went through all mentions of render in the Effect reference docs and replaced it with "commit" when it talked about the timing of the Effect execution.