[css-display] Clarify that run-ins run into things that aren't BFCs; they're okay with other (inline) new formatting contexts. Fixes #1228.

Author: tabatkins

css-display/Overview.bs

@@ -720,7 +720,7 @@ Run-In Layout</h2>
 	<ul>
 		<li>
 			If a <a>run-in sequence</a> is immediately followed by a block box
-			that does not establish a new <a>formatting context</a>,
+			that does not establish a new <a>block formatting context</a>,
 			it is inserted as direct children of the block box
 			after its ''::marker'' pseudo-element's boxes (if any),
 			but preceding any other boxes generates by the contents of the block