[Wi-Fi] Remove 'Do not validate' option in CA certificate spinner

"Do not validate" is not secure and must not be used in any production
network. R Suggestions API already does not allow connections with
no Root CA certificate.

Bug: 162466484
Test: make RunSettingsRoboTests ROBOTEST_FILTER=WifiConfigControllerTest
      make RunSettingsRoboTests ROBOTEST_FILTER=WifiConfigController2Test
      Manually add or edit  an EAP method Wi-Fi network and observe CA
      certificate spinner options.
Change-Id: Ica5ecf8805c51d7cdce7b16e02e0dd79d5f64754
Merged-In: Icf97199967faa2e359b0120a8c989bd1df2c6cea