fix errors on run eventlet with gunicorn

[bergpb]

When I try to start server with gunicorn some errors are showed:

gunicorn wsgi:app --worker-class eventlet -w 1 --timeout 120 --no-sendfile -b 0.0.0.0:8000

Error: class uri 'eventlet' invalid or not found: 

[Traceback (most recent call last):
  File "/home/bergpb/projects/lisapi/.venv/lib/python3.10/site-packages/gunicorn/util.py", line 99, in load_class
    mod = importlib.import_module('.'.join(components))
  File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/home/bergpb/projects/lisapi/.venv/lib/python3.10/site-packages/gunicorn/workers/geventlet.py", line 20, in <module>
    from eventlet.wsgi import ALREADY_HANDLED as EVENTLET_ALREADY_HANDLED
ImportError: cannot import name 'ALREADY_HANDLED' from 'eventlet.wsgi' (/home/bergpb/projects/lisapi/.venv/lib/python3.10/site-packages/eventlet/wsgi.py)
]

[bergpb]

benoitc/gunicorn#2581

[bergpb]

fixed with this tip: https://stackoverflow.com/a/67410245/6539270
still waiting for a new gunicorn version to update