Clarify wording of notification reviewer list

[Eric-Arellano]

Before:

One or more of the the following people are requested to review this:

After:

One or more of the the following people are relevant to this code:

This change is because in practice, most the listed users no longer actually get GitHub notifications. They are only escaped names so that folks know who subject matter experts are.

I avoided adding instructions like "Ping these people if you want help". That's best handled in the prelude and we keep this list concise.

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This PR also updates the README a little.