[Beta] Fix a word from useMemo to useCallback (#5334)

beta/src/content/apis/react/useCallback.md

@@ -348,7 +348,7 @@ button[type="button"] {
 
 In this example, the `ShoppingForm` implementation is also **artificially slowed down** so that you can see what happens when some React component you're rendering is genuinely slow. Try incrementing the counter and toggling the theme.
 
-Unlike in the previous example, toggling the theme is also slow now! This is because **there is no `useMemo` call in this version,** so `handleSubmit` is always a new function, and the slowed down `ShoppingForm` component can't skip re-rendering.
+Unlike in the previous example, toggling the theme is also slow now! This is because **there is no `useCallback` call in this version,** so `handleSubmit` is always a new function, and the slowed down `ShoppingForm` component can't skip re-rendering.
 
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