docs: Fixed diff syntax (#8937)

The blocks with `diff` syntax didn't render correctly. This is a result
of Docusaurus v3 [changing the included languages
](https://docusaurus.io/docs/migration/v3#prism-react-renderer-v20).

website/docusaurus.config.ts

@@ -179,6 +179,7 @@ const config: Config = {
                 'php',
                 'ruby',
                 'bash',
+                'diff',
             ],
         },
         languageTabs: [