Stop limiting the PyYAML version

The old releases of PyYAML does not ship wheels for Python 3.11.
Previously, there was a limitation in place to disallow v6 or higher.

Together with internal `setuptools` deprecations, this caused
`pip install` to fail building PyYAML from sdist. The patch addresses
that by dropping the upper version limit and making `pip` prefer
installing from wheels.

Fixes #64.

action.yml

@@ -223,8 +223,9 @@ runs:
       ;
       python -m
       pip install
-      'PyYAML>5,<6'
+      PyYAML
       --disable-pip-version-check
+      --prefer-binary
       --user
       ;
       set +x