Rename image 2.22

Author: hollasch

books/RayTracingTheNextWeek.html

@@ -2750,7 +2750,7 @@
 <div class='together'>
 We get:
 
-  ![Cornell box with blocks of smoke](../images/img.cornell-smoke.jpg class=pixel)
+  ![Image 22: Cornell box with blocks of smoke](../images/img-2.22-cornell-smoke.jpg class=pixel)
 
 </div>