Remove Connect to public network for Network Rating Provider

According we remove the Network Rating Provider in ag/14675092, and the
Connect to public network item is tied to the Network Rating Provider.
So need to remove together.

Bug: 187119482
Test: Manaul test
      make RunSettingsRoboTests ROBOTEST_FILTER=ConfigureWifiSettingsTest
Change-Id: Ie8a8d5c8d9f2c5db11d6c9e6f84af7864e78814f