fix: correct time format in Python quickstart

[Marc416]

Description

While testing the Calendar API using the Python quickstart guide, I noticed that the time formatting line appends a "Z" to a timezone-aware ISO string. This leads to an invalid ISO 8601 timestamp such as:

2025-04-07T14:39:12.345678+00:00Z

Appending "Z" to a string that already contains +00:00 (UTC offset) makes it invalid and may result in errors when calling the API.

Fix

Updated the time formatting line to remove the redundant "Z":

now = datetime.datetime.now(tz=datetime.timezone.utc).isoformat()

This ensures the timestamp remains valid and conforms to ISO 8601.

Fixes #2115

Has it been tested?

• Development testing done
• Unit or integration test implemented

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have performed a peer-reviewed with team member(s)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[Marc416]

I cannot add reviewers :( @jpoehnelt

[hillro500]

This change fixed an http error code 400 for me, and caused no other issues.

[Marc416]

@PierrickVoulet
Hi PierrickVoulet,
This is Marc. If you have some time, would you mind reviewing this PR?