Drop Py3.8 support

Officially EOL by Python project

Run `poetry update`

Drop "backports.zoneinfo", importlib-resources

Bump time-machine, pytest-codspeed to last version which support Py3.13
https://github.com/adamchainz/time-machine/blob/main/CHANGELOG.rst
https://github.com/CodSpeedHQ/pytest-codspeed/releases

Author: M5oul

README.rst

@@ -11,10 +11,9 @@ Pendulum
     :alt: Pendulum Build status
     :target: https://github.com/sdispater/pendulum/actions
 
-
 Python datetimes made easy.
 
-Supports Python **3.8 and newer**.
+Supports Python **3.9 and newer**.
 
 
 .. code-block:: python