Remove sliceable attribute from biometric preference controllers.

This removes the top-level UI switch on some of the boolean preference settings.

Bug: 193438173
Test: atest com.android.settings.biometrics
Change-Id: If1cd2cb9ae456021fcdf0efc5002db4a083b9689

src/com/android/settings/biometrics/combination/BiometricSettingsAppPreferenceController.java

@@ -86,4 +86,9 @@ public class BiometricSettingsAppPreferenceController extends TogglePreferenceCo
             return AVAILABLE_UNSEARCHABLE;
         }
     }
+
+    @Override
+    public final boolean isSliceable() {
+        return false;
+    }
 }

src/com/android/settings/biometrics/combination/BiometricSettingsKeyguardPreferenceController.java

@@ -68,4 +68,9 @@ public class BiometricSettingsKeyguardPreferenceController extends TogglePrefere
         }
         return getRestrictingAdmin() != null ? DISABLED_FOR_USER : AVAILABLE;
     }
+
+    @Override
+    public final boolean isSliceable() {
+        return false;
+    }
 }