Remove plone prefix from @site endpoint

The https://demo.plone.org/++api++/@site returns the following data:

{
  "@id": "https://demo.plone.org/@site", 
  "features": {
    "filter_aliases_by_date": true, 
    "multilingual": false
  }, 
  "plone.allowed_sizes": [
    "icon 32:32", 
    "tile 64:64", 
    "thumb 128:128", 
    "mini 200:65536", 
    "preview 400:65536", 
    "teaser 600:65536", 
    "large 800:65536", 
    "larger 1000:65536", 
    "great 1200:65536", 
    "huge 1600:65536"
  ], 
  "plone.available_languages": [
    "en"
  ], 
  "plone.default_language": "en", 
  "plone.portal_timezone": "UTC", 
  "plone.robots_txt": "Sitemap: {portal_url}/sitemap-index.xml\n\n# Define access-restrictions for robots/spiders\n# http://www.robotstxt.org/wc/norobots.html\n\nUser-agent: *\nDisallow: /search\nDisallow: /login\n\n# Add Googlebot-specific syntax extension to exclude forms\n# that are repeated for each piece of content in the site\n# the wildcard is only supported by Googlebot\n# http://www.google.com/support/webmasters/bin/answer.py?answer=40367&ctx=sibling\n\nUser-Agent: Googlebot\nDisallow: /*login\nDisallow: /*search\nDisallow: /*edit\n", 
  "plone.site_logo": null, 
  "plone.site_title": "Plone 6 Demo Site"
}

The plone. prefix is not needed and is an implementation detail.

Start by locating the implementation and tests for the ++api++/@site endpoint described in the issue. Verify the response fields that currently use the plone. prefix, then update the endpoint so those fields are returned without it and confirm the response matches the documented example.