[css-rhythm] fix markup of new figures

Author: dauwhe

css-rhythm/Overview.bs

@@ -237,18 +237,19 @@ Adjusting Block-level Box Heights {#block-height}
 	Constraining block height, rather than line height, to a multiple of a step size 
 	can achieve a vertical rhythm in these circumstances.
 
-	<div class="example">
+
 		<div class="figure">
 			<img src="images/block-step-size-before.png"
-			style="width: 600px">
+			style="width: 500px">
 			<figcaption>Heads and blockquotes have varying font sizes and line heights, 
 			resulting in uneven text across columns.</figcaption>
 		</div>
-		
-	<div class="example">
+
+
+
 		<div class="figure">
 			<img src="images/block-step-size-after.png"
-			style="width: 600px">
+			style="width: 500px">
 			<figcaption>Space inserted before and after blocks (shown with colored borders) 
 			restores vertical rhythm.</figcaption>
 		</div>