Change 'requires' to 'install_requires' in setup.py

[RomainL972]

The runtime dependencies should be in "install_requires". "requires" is for build dependencies. Otherwise, the "requests" package won't correctly be installed when running "pip install python-powerdns" in a clean environment:

Python 3.10.12 (main, Aug 15 2025, 14:32:43) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import powerdns
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/romain/.../venv/lib/python3.10/site-packages/powerdns/__init__.py", line 26, in <module>
    from .client import PDNSApiClient
  File "/home/romain/.../venv/lib/python3.10/site-packages/powerdns/client.py", line 27, in <module>
    import requests
ModuleNotFoundError: No module named 'requests'

Reference