[SB][Wifi] Remove unused networkId from WifiNetworkModel classes.

The network ID is no longer used anywhere now that we've moved to
WifiTrackerLib, so this CL removes it from WifiNetworkModel.Active and
WifiNetworkModel.CarrierMerged.

Bug: 292534484
Flag: EXEMPT refactor
Test: atest WifiRepositoryImplTest WifiInteractorImplTest
Test: smoke test of the wifi icon and Internet tile
Change-Id: I0261a9883d5baec2c5e797b42f9bb36e91ff2b92