Update docs on creating redirects (#20806)

docs/contributing/docs-contributions.md

@@ -109,14 +109,11 @@ Sometimes it makes sense to move or rename a file as part of docs restructuring
 
 - Run proposed structure changes by the Gatsby docs team in [a GitHub issue](/contributing/how-to-file-an-issue/) to ensure your change is accepted.
 - Update all instances of the old URL to your new one. [Find and replace](https://code.visualstudio.com/docs/editor/codebasics#_search-across-files) in VS Code can help. Check that the context of the original link reference still makes sense with the new one.
-- For SEO purposes, add a redirect to the `createPages` function in [`www/gatsby-node.js`](https://github.com/gatsbyjs/gatsby/tree/master/www/gatsby-node.js). Here's an example:
-
-```js:title=www/gatsby-node.js
-createRedirect({
-  fromPath: `/docs/source-plugin-tutorial/`,
-  toPath: `/docs/pixabay-source-plugin-tutorial/`,
-  isPermanent: true,
-})
+- For SEO purposes, add a redirect to [`www/redirects.yaml`](https://github.com/gatsbyjs/gatsby/tree/master/www/redirects.yaml). Here's an example:
+
+```yaml:title=www/redirects.yaml
+- fromPath: /docs/source-plugin-tutorial/
+  toPath: /docs/pixabay-source-plugin-tutorial/
 ```
 
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