LibWeb: Stub out Fetch::Infrastructure::Body::clone()

Author: https://github.com/linusg
Commit: a7164f2674
Pull-request: https://github.com/SerenityOS/serenity/pull/15359
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/davidot ✅
Reviewed-by: https://github.com/kennethmyhra

Userland/Libraries/LibWeb/Fetch/Infrastructure/HTTP/Requests.h

@@ -287,7 +287,7 @@ public:
     [[nodiscard]] String serialize_origin() const;
     [[nodiscard]] ErrorOr<ByteBuffer> byte_serialize_origin() const;
 
-    [[nodiscard]] NonnullOwnPtr<Request> clone() const;
+    [[nodiscard]] WebIDL::ExceptionOr<NonnullOwnPtr<Request>> clone() const;
 
     [[nodiscard]] ErrorOr<void> add_range_reader(u64 first, Optional<u64> const& last);