Update adding-custom-styles.mdx

Author: adamwathan

src/pages/docs/adding-custom-styles.mdx

@@ -119,7 +119,7 @@ This can be useful for things like CSS variables as well, especially when they n
 
 ### Arbitrary variants
 
-Arbitrary _variants_ are like arbitrary values but for doing on-the-fly selector modification, like you can with built-in pseudo-class variants like `hover:{utility}` or responsive variants `md:{utility}` but using square bracket notation directly in your HTML.
+Arbitrary _variants_ are like arbitrary values but for doing on-the-fly selector modification, like you can with built-in pseudo-class variants like `hover:{utility}` or responsive variants like `md:{utility}` but using square bracket notation directly in your HTML.
 
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