documentation fix (#804)

Author: daikazu

src/pages/docs/grayscale.mdx

@@ -20,10 +20,10 @@ export const classes = {
 
 ## Usage
 
-Use the `grayscale` and `grayscale-0` utilities alongside the `backdrop-filter` utility to whether an element should be rendered as grayscale or in full color.
+Use the `grayscale` and `grayscale-0` utilities alongside the `filter` utility to whether an element should be rendered as grayscale or in full color.
 
 ```html
-<div class="backdrop-filter grayscale ...">
+<div class="filter grayscale ...">
   <!-- ... -->
 </div>
 ```