Fix compatibility with Dart Sass 3.0.0

[mir-jalu]

Deprecation Warning [global-builtin]: Global built-in functions are deprecated and will be removed in Dart Sass 3.0.0.
Use meta.function-exists instead.

More info and automated migrator: https://sass-lang.com/d/import

   ╷
35 │     @if function-exists(font-url) {

[markvantilburg]

@ahmadalfy can you merge this one

[ahmadalfy]

I think this is a breaking change. We can release it with the planned jQuery 4 release.