Remove the flag for the SharedConnectivityManager.getBroadcastReceiver() method.

TestApis don't need flags and this feature already shipped.

Change-Id: Ib848fb9e98fda533145b7df9f24670fc98f45351
Fixes: 378546519
Test: atest SharedConnectivityManagerTest
Flag: EXEMPT removing FLAG_SHARED_CONNECTIVITY_BROADCAST_RECEIVER_TEST_API