[css-grids-1][editorial] Markup fix, closes w3c#5626

Author: tabatkins

css-grid-1/Overview.bs

@@ -3962,7 +3962,7 @@ Track Sizing Algorithm</h3>
 		<li>[[#algo-content|Resolve Intrinsic Track Sizes]]
 		<li>[[#algo-grow-tracks|Maximize Tracks]]
 		<li>[[#algo-flex-tracks|Expand Flexible Tracks]]
-		<li>[[#algo-stretch|Expand Stretched <css>auto</css> Tracks]]
+		<li><a section href=#algo-stretch>Expand Stretched <css>auto</css> Tracks</a>
 	</ol>
 
 <h3 id="algo-init">