Fix CI: Change assert self.app.timezone.zone to assert self.app.timezone.key

[stasfilin]

Good afternoon,
This Pull Request is a quick fix for CI.

The error message AttributeError: 'zoneinfo.ZoneInfo' object has no attribute 'zone'

So, we can use
self.app.timezone.key

[auvipy]

thanks for the PR. will merge after CI is green

[stasfilin]

@auvipy Good morning

I see that the lint is failed

Failed to reach any of the inventories with the following issues:

  intersphinx inventory 'https://celery.readthedocs.io/en/master/objects.inv' not fetchable due to <class 'requests.exceptions.HTTPError'>: 404 Client Error: Not Found for URL: https://docs.celeryq.dev/en/mastethe lint is failed 



This one is strange. Do you know the new URL that we need to use?

Thanks

[auvipy]

Instead of https://celery.readthedocs.io/en/master/ this should be https://celery.readthedocs.io/en/main/

[stasfilin]

@auvipy Hi again, I did changes

[auvipy]

all green. thanks Stanislav