[css-grid] Update figure numbers. Fixes #1278

Author: fantasai

css-grid/Overview.bs

@@ -217,7 +217,7 @@ Adapting Layouts to Available Space</h4>
 			 *  1. the first sized to content,
 			 *  2. the second receives the remaining space
 			 *     (but is never smaller than the minimum size of the board
-			 *     or the game controls, which occupy this column [Figure 3])
+			 *     or the game controls, which occupy this column [Figure 4])
 			 *
 			 * Three rows:
 			 *  3. the first sized to content,
@@ -278,7 +278,7 @@ Source-Order Independence</h4>
 
 	Continuing the prior example,
 	the author also wants the game to adapt to different devices.
-	Also, the game should optimize the placement of the components when viewed either in portrait or landscape orientation (Figures 4 and 5).
+	Also, the game should optimize the placement of the components when viewed either in portrait or landscape orientation (Figures 6 and 7).
 	By combining grid layout with media queries,
 	the author is able to use the same semantic markup,
 	but rearrange the layout of elements independent of their source order,