* gnu/packages/python-xyz.scm (python-celery): Update to 5.3.6.
[build-system]: Use pyproject-build-system.
[arguments]: Replace pytz with tzdata in the relax-requirements phase. Do not
override the check phase, skip tests in #:test-flags instead.
[native-inputs]: Add python-pytest-click.
[propagated-inputs]: Add python-tzdata. Remove python-pytz.
Change-Id: I4cb6a1c6712d5b54f4d9a6731447e9459e8ff81a
dbe16f5a68