devel/py-hologram: fix packaging

It's a direct commit. py-python-dateutil is not in the 2024Q2, so change
it back to py-dateutil while preserving required version limitation change.

Approved by: portmgr (antoine)
Differential Revision: https://reviews.freebsd.org/R11:eb44fa832b1272ee0eb8273e13bc2dac348278c2