Remove NetworkPolicyManager listener.

Now that we're using only asynchronous connectivity APIs, we no longer
need to listen to changes directly from NPMS to trigger evaluations.

Bug: 141645789
Bug: 142281756
Test: atest CtsJobSchedulerTestCases:ConnectivityConstraintTest
Test: atest CtsJobSchedulerTestCases:JobThrottlingTest
Test: atest FrameworksMockingServicesTests:ConnectivityControllerTest
Change-Id: Ia42f775cf1171e251956ad711f4cbdcbc0ebd20c