Improve concision in Efficiency-for-the-right-group

Why is this change being made?

Attempting to make Efficiency for the right group more succinct. There is no intention to change the value itself. The original paragraph outlines the concept, then gives a conceptual example, then gives a concrete example. In my opinion, the conceptual example adds very little value and so I'm proposing it be removed.

Does this MR meet the acceptance criteria?

Sorry, I don't know. I struggled to find docs on the acceptance criteria, (I found plenty of links to contributing to the acceptance criteria, but not the criteria itself). I'm working under the assumption that a text change in a .md file should be safe, but maybe that's a bad assumption. I wrote the same thing in my other MR

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what