fix: update contributing file reference (#6351)

## What's the problem this PR addresses?

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PR #6133 renamed the contributing file. This PR adjusts sources to
changes.

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...

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Signed-off-by: Emmanuel Ferdman <[email protected]>

Author: emmanuel-ferdman

packages/docusaurus/docs/advanced/04-technical/contributing.mdx

@@ -129,7 +129,7 @@ It's generally seen as [bad form](https://twitter.com/brian_d_vaughn/status/1224
 
 We use [Docusaurus](https://docusaurus.io/docs) to generate HTML pages from [mdx](https://mdxjs.com/docs/) sources files.
 
-Our website is stored within the [`packages/docusaurus`](https://github.com/yarnpkg/berry/tree/master/packages/docusaurus) directory. You can change a page by modifying the corresponding `.mdx` file in the `docs` folder. For example, you'd edit this very page [here](https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/contributing.md).
+Our website is stored within the [`packages/docusaurus`](https://github.com/yarnpkg/berry/tree/master/packages/docusaurus) directory. You can change a page by modifying the corresponding `.mdx` file in the `docs` folder. For example, you'd edit this very page [here](https://github.com/yarnpkg/berry/blob/master/packages/docusaurus/docs/advanced/04-technical/contributing.mdx).
 
 Then run the following command to spawn a local server and see your changes: