Remove platform key when user disables lock screen protection

Correctly sync keys on LSKF update.

Bug: 72443379
Test: adb shell am instrument -w -e package
com.android.server.locksettings.recoverablekeystore
com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner

Change-Id: I2569310388a6f852c86d560663024d8c8dadb761