[css-grid] Remove mention of flexing.

Author: tabatkins

css-grid/Overview.html

@@ -2533,7 +2533,7 @@ <h3 id=auto-margins><span class=secno>7.1. </span> Aligning with ‘<a
 
   <p class=note> Note that, if free space is distributed to auto margins, the
    alignment properties will have no effect in that dimension because the
-   margins will have stolen all the free space left over after flexing.
+   margins will have stolen all the free space left over after sizing.
 
   <div class=example> TODO: EXAMPLE HERE</div>
 

css-grid/Overview.src.html

@@ -1991,7 +1991,7 @@ <h3 id='auto-margins'>
 		Note that, if free space is distributed to auto margins, 
 		the alignment properties will have no effect in that dimension
 		because the margins will have stolen all the free space
-		left over after flexing.
+		left over after sizing.
 
 	<div class='example'>
 		TODO: EXAMPLE HERE