LibWeb: Use resources to find internal HTML template paths

Author: https://github.com/bplaat
Commit: 009729d5e3
Pull-request: https://github.com/SerenityOS/serenity/pull/22437
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibWeb/Loader/GeneratedPagesLoader.h

@@ -11,11 +11,6 @@
 
 namespace Web {
 
-String error_page_url();
-void set_error_page_url(String);
-String directory_page_url();
-void set_directory_page_url(String);
-
 ErrorOr<String> load_error_page(AK::URL const&);
 
 ErrorOr<String> load_file_directory_page(AK::URL const&);