Update class-kirki-modules.php to fix bedrock compat

[Levdbas]

When using Bedrock the WordPress folders are placed in a /wp/ folder. Using site_url() points to that /wp/ folder. Since this is a hook that we want to call directly to the front-end we need to use home_url() instead.

This fixes the issuse where this hook causes a 404 in the backend:

Fixes: https://github.com/kirki-framework/kirki/issues/2365