📝 Docs: Remove Matomo from the website

[JoshuaKGoldberg]

Documentation Request Checklist

• I have read and agree to Mocha's Code of Conduct and Contributing Guidelines
• I have searched for related issues and issues with the faq label, but none matched my issue.
• I want to provide a PR to resolve this

Overview

We don't need the analytics and don't want to collect user data. Let's remove it. 🔪

Additional Info

No response

[JoshuaKGoldberg]

TIL https://mochajs.matomo.cloud exists and is public. It's not referenced in our repo anywhere and we don't have any Netlify integrations. So I don't know how this is getting added to the site:

<!-- Matomo -->
<script type="text/javascript">
  var _paq = _paq || [];
  /* tracker methods like "setCustomDimension" should be called before "trackPageView" */
  _paq.push(['trackPageView']);
  _paq.push(['enableLinkTracking']);
  (function() {
    var u="https://mochajs.matomo.cloud/";
    _paq.push(['setTrackerUrl', u+'piwik.php']);
    _paq.push(['setSiteId', '1']);
    var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0];
    g.type='text/javascript'; g.async=true; g.defer=true; g.src=u+'piwik.js'; s.parentNode.insertBefore(g,s);
  })();
</script>
<!-- End Matomo Code -->

This might be something in Cloudflare. Which I don't have access to yet. Marking as blocked.