[css-grid] Make the edit I was supposed to do last year from https://lists.w3.org/Archives/Public/www-style/2015Sep/0032.html , clamping the flex factor to 1 in the indefinite case as well.

Author: tabatkins

css-grid/Overview.bs

@@ -4067,7 +4067,10 @@ Stretch Flexible Tracks</h3>
 
 			<ul>
 				<li>
-					Each flexible track's <a>base size</a> divided by its <a>flex factor</a>.
+					If the flexible track's <a>flex factor</a> is greater than one,
+					the result of dividing the track's <a>base size</a> by its <a>flex factor</a>;
+					otherwise,
+					the track's <a>base size</a>.
 
 				<li>The result of
 					<a href="#algo-find-fr-size">finding the size of an fr</a>