-moz-osx-font-smoothing css media query leaks OS information

This issue was last mentioned and fixed here: legacy/trac#13016 (moved)

However, the query still works in the latest version of Tor Browser.

Steps to recreate:

if (CSS.supports('-moz-osx-font-smoothing', 'inherit')) {
    console.log('MacOS user')
} else {
    console.log('Not MacOS user')
}

This can also be modified to work without javascript using something like this,

@supports(-moz-osx-font-smoothing: inherit) {
  .example {
    background: url(...);
  }
}

which would send an html request on MacOS browsers