chore: ignore website docs generated in biome (#9168)

https://linear.app/unleash/issue/2-3208/add-website-docs-generated-folder-to-biome-ignore-lists

Noticed when running `yarn lint` locally that we get this error:

```
./website/docs/generated/openapi.json format ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Size of ./website/docs/generated/openapi.json is 1.7 MiB which exceeds configured maximum of 1.0 MiB for this project.
    The file size limit exists to prevent us inadvertently slowing down and loading large files that we shouldn't.
    Use the `files.maxSize` configuration to change the maximum size of files processed.
```

To overcome this, this PR adds `website/docs/generated` to the ignore
list of both the linter and formatter in our Biome settings.

biome.json

@@ -49,6 +49,7 @@
       "docker",
       "bundle.js",
       "website/build",
+      "website/docs/generated",
       "website/global.js",
       "setupJest.js",
       "dist",
@@ -79,6 +80,7 @@
       "src/test/examples/*.json",
       "coverage",
       "website/build",
+      "website/docs/generated",
       "website/global.js",
       ".docusaurus",
       "./package.json",