[1.23] testing commit (13d5ba3) fails do to missing websockets

[Alexander Balderson]

the requirements.txt/.in files result in a a conflict on websockets for python 3.8 resulting in websockets 7 getting installed, and then uninstalled right before testing

Uninstalling websockets-7.0:
  Successfully uninstalled websockets-7.0
py3 run-test: commands[2] | pytest -v -s --junit-xml=/home/ubuntu/project/generated/kubernetes/k8s-suite/test_status_messages-junit.xml --controller=foundations-aws --model=kubernetes /home/ubuntu/k8s-validation/jobs/integration/validation.py::test_status_messages
ImportError while loading conftest '/home/ubuntu/k8s-validation/jobs/integration/conftest.py'.
jobs/integration/conftest.py:15: in <module>
    from juju.model import Model
.tox/py3/lib/python3.8/site-packages/juju/model.py:22: in <module>
    import websockets
E ModuleNotFoundError: No module named 'websockets'

[Adam Dyess (addyess)]

added environment markers to requirements.txt to address issues installing websockets package
https://github.com/charmed-kubernetes/jenkins/commit/13d5ba3add8cb1b532336d39418131ab1f0e8709

These must be maintained in the charmed-kubernetes requirements.txt unless

# The following websocket requirements are environment marked because of juju
# https://github.com/juju/python-libjuju/blob/master/setup.py#L38-L39
websockets==7.0 ; python_version < "3.9"
websockets==8.0 ; python_version >= "3.9"