Revert "Pin oslo.policy<=3.4.0"

It broke e.g ceilometer/aodh on devstack.
This reverts commit a2d84f5.

Resolves: #1095
(cherry picked from commit 6937eff)

setup.cfg

@@ -28,10 +28,7 @@ install_requires =
     numpy>=1.9.0
     iso8601
     oslo.config>=3.22.0
-    # TODO(tobias-urdin): oslo.policy >= 3.5.0 requires
-    # PyYAML>=5.1 which something we use blocks. Need
-    # to fix this to support Ubuntu Focal later.
-    oslo.policy>=0.3.0,<=3.4.0
+    oslo.policy>=0.3.0
     oslo.middleware>=3.22.0
     pytimeparse
     pecan>=0.9