Fix PostCommit Python Xlang IO Dataflow job (#35638)

* Pin tox version to 4.27.0

* Change dependency restriction

Author: Amar3tto

sdks/python/setup.py

@@ -478,7 +478,9 @@ def get_portability_package_data():
               # --extra-index-url or --index-url in requirements.txt in
               # Dataflow, which allows installing python packages from private
               # Python repositories in GAR.
-              'keyrings.google-artifactregistry-auth'
+              'keyrings.google-artifactregistry-auth',
+              # tox dependency which doesn't conflict with cachetools<6
+              'tox<4.28.0'
           ],
           'interactive': [
               'facets-overview>=1.1.0,<2',