LibWeb: Move extract_body() towards spec compliance

Author: https://github.com/kennethmyhra
Commit: 9b3da5a142
Pull-request: https://github.com/SerenityOS/serenity/pull/14595
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibWeb/XHR/XMLHttpRequest.h

@@ -38,11 +38,6 @@ public:
         Done = 4,
     };
 
-    struct BodyWithType {
-        ByteBuffer body;
-        String type;
-    };
-
     using WrapperType = Bindings::XMLHttpRequestWrapper;
 
     static NonnullRefPtr<XMLHttpRequest> create(HTML::Window& window)