LibWeb: Update 'default.css' for 'audio' element UA rule with no control

[Ahmad-S792]

Hi Folks,

I noticed that all browsers have following rule in their UA stylesheets:

audio:not([controls]) {
  display: none !important;
}

It is not in web-spec directly as 'UA' stylesheet recommendation but it is in web-spec:

https://html.spec.whatwg.org/#embedded-content-rendering-rules

"When an audio element is not exposing a user interface, the user agent is expected
to force its 'display' property to compute to 'none', irrespective of CSS rules."

I added it late in WebKit (shipped in Safari 16.4), so it would be good to add it straight-away and get away from 'BrowserCompat' issue.

Just wanted to raise so it can be at least tracked. I can do PR to add but I cannot test it (like compile etc.).

Thanks!