[docs] Broken translation pages

[oliviertassinari]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

The translation pages are broken.

Expected Behavior 🤔

It works

Steps to Reproduce 🕹

• Open https://material-ui.com/pt/components/data-grid/
• If you are coming with a browser that is configured to accept Chinese, Portuguese or Russian by default, it auto-redirect to the broken page.

Context

We could probably solve this by redirecting the languages to the English content as a quick workaround.
Then later, we could bring the translation stack from the main repository. Since the work @mbrookes has done on Crowdin infrastructure, it could potentially be easy to setup.

Thanks @dmtrKovalenko for the report.