[css-display] Move note per #1185.

Author: fantasai

css-display/Overview.bs

@@ -887,15 +887,19 @@ Appendix A: Glossary</h2>
 			as determined by the constraints of other properties
 			(such as 'overflow' or 'align-content').
 
-			Note: Not all block container boxes are block-level boxes:
-			non-replaced inline blocks and non-replaced table cells are block containers
-			but not block-level boxes.
-			Block-level boxes that are also block containers are called <a>block boxes</a>.
-
 		<dt><dfn>block box</dfn>
 		<dd>
 			A <a>block-level box</a> that is also a <a>block container</a>.
 
+			Note: Not all <a>block container</a> boxes are <a>block-level</a> boxes:
+			non-replaced inline blocks and non-replaced table cells,
+			for example, are block containers
+			but not block-level boxes.
+			Similarly, not all block-level boxes are block containers:
+			block-level replaced elments (''display: block'')
+			and flex containers (''display: flex''), for example,
+			are not block containers.
+
 		<dt><dfn>block</dfn>
 		<dd>
 			Used as a shorthand for <a>block box</a>, <a>block-level box</a>, or <a>block container box</a>,