[AAPM] Remove unreleased WEP feature.

This feature was developed for Android B but never released. This change
removes UI related code for the feature, and references to the AAPM
flag.

Bug: 433316458
Bug: 352420507
Test: atest AdvancedProtectionServiceTest SettingsLibWifiUtilsTest
InternetAdapterTest ActionDisabledByAdvancedProtectionDialogTest
WepNetworksPreferenceControllerTest SpaUnitTests
Flag: EXEMPT FLAG_REMOVAL

Change-Id: I07ffcc28c80589357beee22a17355e5e674ebf7e