protobuf: build with up-to-date dateutil

Fixes #32571. @mistydemeo, can you take a look / try this?
Ah, I see. Yeh, I'm not sure I agree with this approach; I think it makes sense to do for applications but not really for stuff that installs libraries. #32571 is regrettable but I consider is expected behaviour; it's what you'd get when installing from outside Homebrew too.