Forgotten import statement for createElement (#5601)

Added `createElement` in the import statement since it was used within the code snippet but was not imported.

beta/src/content/reference/react/isValidElement.md

@@ -23,7 +23,7 @@ const isElement = isValidElement(value)
 Call `isValidElement(value)` to check whether `value` is a React element.
 
 ```js
-import { isValidElement } from 'react';
+import { isValidElement, createElement } from 'react';
 
 // ✅ React elements
 console.log(isValidElement(<p />)); // true