suggestion: add back the "key moves" label in the AI Review component

[teauxfu]

Some screenshots in the docs from earlier versions show this "key moves" label, I haven't done a git blame yet but it looks like it was intentionally removed from the markup at some point. I think the label was useful. I figured out what the buttons were for eventually, but as a brand-new user it was kind of confusing.

I wanted to ask if there were any particular reasons for removing it, and to see how we felt about bringing it back?

https://github.com/online-go/online-go.com/wiki/Understanding-the-AI-review#the-graph

online-go.com/src/components/AIReview/AIReview.tsx

Lines 563 to 571 in 1c52f40

	<div className="worst-moves-container">
	<WorstMovesList
	moves={worst_move_list}
	onMoveClick={(moveNumber) =>
	gobanController.gotoMove(moveNumber)
	}
	maxMovesShown={WORST_MOVES_SHOWN}
	/>
	</div>