Remove default override for config options policy_file

olso.policy 4.5.0[1] changed the config options policy_file
default value to 'policy.yaml', which means it is changed
for all the OpenStack services and they do not need to
override the default anymore.

NOTE: There is no change in behaviour here, oslo.policy provides
the same configuration that services have overridden till now.

[1] https://review.opendev.org/c/openstack/releases/+/934012
[2] https://review.opendev.org/c/openstack/requirements/+/934295

Change-Id: I46cc9e05fbc8f6c95c0b2d50093ecfb070a4170f

requirements.txt

@@ -18,7 +18,7 @@ oslo.db>=4.44.0 # Apache-2.0
 oslo.i18n>=3.20.0 # Apache-2.0
 oslo.log>=3.37.0 # Apache-2.0
 oslo.messaging>=14.1.0 # Apache-2.0
-oslo.policy>=3.6.0 # Apache-2.0
+oslo.policy>=4.5.0 # Apache-2.0
 oslo.reports>=1.27.0 # Apache-2.0
 oslo.serialization>=2.25.0 # Apache-2.0
 oslo.service>=1.30.0 # Apache-2.0

watcher/common/policy.py

@@ -18,7 +18,6 @@
 import sys
 
 from oslo_config import cfg
-from oslo_policy import opts
 from oslo_policy import policy
 
 from watcher.common import exception
@@ -27,12 +26,6 @@ from watcher.common import policies
 _ENFORCER = None
 CONF = cfg.CONF
 
-# TODO(gmann): Remove setting the default value of config policy_file
-# once oslo_policy change the default value to 'policy.yaml'.
-# https://github.com/openstack/oslo.policy/blob/a626ad12fe5a3abd49d70e3e5b95589d279ab578/oslo_policy/opts.py#L49
-DEFAULT_POLICY_FILE = 'policy.yaml'
-opts.set_defaults(CONF, DEFAULT_POLICY_FILE)
-
 
 # we can get a policy enforcer by this init.
 # oslo policy support change policy rule dynamically.