Add instruction on observing reviewer status roulette comment

What does this MR do and why?

Add instruction on observing reviewer status roulette comment

• sometimes roulette suggests a reviewer and by the time the author of the MR is ready to review, they are busy. This can be due to their limit on number of reviews they have assigned at once. We should add some verbiage to help guide MR authors to observe this.

Scenario that brought this up:

I have 2️⃣ set on my status, which means I only want to have 2 reviews assigned at the same time.

Today when I logged in to work, I had 4 assigned. I assume that can happen for a few reasons, but one of them is that roulette will pick me as long as I'm under 2 reviews currently assigned.

Therefore, if I have been picked 4 times and only have 1 MR currently assigned, then it would be likely I'll get over 2 reviews assigned at some point.

The status indicator on the roulette assignment, as seen below, is meant to give more of a realtime assessment of my availability. This MR will help encourage observing it.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.