[css-images-3] optimizeSpeed aliases pixelated.

Author: tabatkins

css-images-3/Overview.bs

@@ -1920,7 +1920,7 @@ Determing How To Scale an Image: the 'image-rendering' property {#the-image-rend
 	This property previously accepted the values ''optimizeSpeed'' and ''optimizeQuality''.
 	These are now deprecated;
 	a user agent must accept them as valid values
-	but must treat them as having the same behavior as ''image-rendering/auto'',
+	but must treat them as having the same behavior as ''pixelated'' and ''image-rendering/auto'' respectively,
 	and authors must not use them.