[v4.4.1-rhel] Fix AttributeError: cython_sources

Apparent Cython regression causing a warning and traceback when
installing PyYAML with pip:

Ref. Upstream issue 601: https://github.com/yaml/pyyaml/issues/

Ref. warning message:
```
********************************************************************************
The license_file parameter is deprecated, use license_files instead.
By 2023-Oct-30, you need to update your project and remove deprecated calls
or your builds will no longer be supported.
See https://setuptools.pypa.io/en/latest/userguide/declarative_config.html for details.
********************************************************************************
```

Ref. traceback snippet:
```
Traceback (most recent call last):
  File "/var/tmp/go/src/github.com/containers/podman/venv/lib/python3.10/site-packages/pip/_vendor/pyproject_hooks/_in_process/_in_process.py", line 353, in <module>
    main()
...cut...
  File "<string>", line 201, in get_source_files
  File "/tmp/pip-build-env-yiijk0jv/overlay/lib/python3.10/site-packages/setuptools/_distutils/cmd.py", line 107, in __getattr__
    raise AttributeError(attr)
AttributeError: cython_sources
```

Signed-off-by: Chris Evich <[email protected]>

<MH: Cherry-pick back to v4.4.1-rhel>

Signed-off-by: Matt Heon <[email protected]>

test/apiv2/python/requirements.txt

@@ -2,4 +2,4 @@ requests-mock~=1.9.3
 requests~=2.20.0
 setuptools~=50.3.2
 python-dateutil~=2.8.1
-PyYAML~=5.4.1
+PyYAML==6.0.1

test/python/requirements.txt

@@ -3,4 +3,4 @@ requests-mock~=1.9.3
 requests~=2.20.0
 setuptools~=50.3.2
 python-dateutil~=2.8.1
-PyYAML~=5.4.1
+PyYAML==6.0.1