chore(babel-preset-gatsby): fix broken link to optimize-hook-destruct…

…uring (#27350)

- previously it pointed to an actual package, however, there is no such
  package and so this link 404'd
  - looking through the blames, this seems to be a plugin implemented
    within preset-gatsby itself, not as a separate package
    - point to correct location there instead
    - would probably be good to have a separate package for it though!

packages/babel-preset-gatsby/README.md

@@ -15,7 +15,7 @@ For more information on how to customize the Babel configuration of your Gatsby
 - [`babel-plugin-transform-react-remove-prop-types`](https://github.com/oliviertassinari/babel-plugin-transform-react-remove-prop-types)
 - [`@babel/plugin-proposal-nullish-coalescing-operator`](https://babeljs.io/docs/en/babel-plugin-proposal-nullish-coalescing-operator)
 - [`@babel/plugin-proposal-optional-chaining`](https://babeljs.io/docs/en/babel-plugin-proposal-optional-chaining)
-- [`babel-plugin-optimize-hook-destructuring`](https://www.github.com/gatsbyjs/gatsby/packages/babel-plugin-optimize-hook-destructring)
+- [`babel-plugin-optimize-hook-destructuring`](src/optimize-hook-destructuring.ts)
 
 ## Usage