Update saturation description (cloudflare#17882)

Author: dcpena

src/content/partials/images/saturation.mdx

@@ -3,7 +3,7 @@
 ---
 import { Tabs, TabItem } from "~/components"
 
-Increases saturation by a factor. A value of `1.0` equals no change, a value of `0.5` equals half saturation, and a value of `2.0` equals twice as saturated. `0` is ignored.
+Increases saturation by a factor. A value of `1.0` equals no change, a value of `0.5` equals half saturation, and a value of `2.0` equals twice as saturated. A value of `0` will convert the image to grayscale.
 
 <Tabs>
   <TabItem label="URL format">
@@ -16,4 +16,4 @@ Increases saturation by a factor. A value of `1.0` equals no change, a value of
   cf: {image: {saturation: 0.5}}
   ```
   </TabItem>
-</Tabs>
+</Tabs>