Fix upgrading broken link (vercel#23785)

Fix a broken link in the [upgrading documentation](https://github.com/vercel/next.js/blob/canary/docs/upgrading.md).

docs/upgrading.md

@@ -6,7 +6,7 @@ description: Learn how to upgrade Next.js.
 
 ## React 16 to 17
 
-React 17 introduced a new [JSX Transform](https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) that brings a long-time Next.js feature to the wider React ecosystem: Not having to `import React from 'react'` when using JSX. When using React 17 Next.js will automatically use the new transform. This transform does not make the `React` variable global, which was an unintended side-effect of the previous Next.js implementation. A [codemod is available](/docs/advanced-features/codemods#add-missing-react-import) to automatically fix cases where you accidentally used `React` without importing it.
+React 17 introduced a new [JSX Transform](https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) that brings a long-time Next.js feature to the wider React ecosystem: Not having to `import React from 'react'` when using JSX. When using React 17 Next.js will automatically use the new transform. This transform does not make the `React` variable global, which was an unintended side-effect of the previous Next.js implementation. A [codemod is available](/docs/advanced-features/codemods.md#add-missing-react-import) to automatically fix cases where you accidentally used `React` without importing it.
 
 ## Upgrading from version 9 to 10