[css-display-3] Improve antecedenting and punctuation.

Author: fantasai

css-display-3/Overview.bs

@@ -846,7 +846,7 @@ Run-In Layout</h2>
 		<li>
 			If a <a>run-in sequence</a> is immediately followed by a block box
 			that does not establish a new <a>block formatting context</a>,
-			it is inserted as direct children of the block box
+			it is inserted as direct children of that block box:
 			after its ''::marker'' pseudo-element's boxes (if any),
 			but preceding any other boxes generated by the contents of the block
 			(including the box generated by the ''::before'' pseudo-element, if any).