Remove sendNetworkConditionsBroadcast

sendNetworkConditionsBroadcast is removed, so
TestNetworkStackService.kt cannot override it anymore,
otherwise there will be a build break when running this
test.
Also add a comment for NETWORK_CONDITIONS_MEASURED in
AndroidManifest.xml.

Bug: 175213041
Test: atest FrameworksNetIntegrationTests
Change-Id: I7b43940dc32826c70fa82f471b35bc5cb8394aad