Fix AmbientDisplayAlwaysOn isSliceable.

I changed this method to return true in ag/22761786 thinking that it was
necessary (as per the example at
https://g3doc.corp.google.com/company/teams/apps-android-settings/howto/settings_slices.md#preference-controller),
but this breaks a test, so I'm rolling back that part of the change.

Fix: 279881487
Test: presubmit
Change-Id: I87716a0daf5face9a79f98353b49ea2166226279

src/com/android/settings/display/AmbientDisplayAlwaysOnPreferenceController.java

@@ -22,6 +22,7 @@ import android.os.PowerManager;
 import android.os.SystemProperties;
 import android.os.UserHandle;
 import android.provider.Settings;
+import android.text.TextUtils;
 
 import androidx.preference.Preference;
 
@@ -63,7 +64,7 @@ public class AmbientDisplayAlwaysOnPreferenceController extends TogglePreference
 
     @Override
     public boolean isPublicSlice() {
-        return true;
+        return TextUtils.equals(getPreferenceKey(), "ambient_display_always_on");
     }
 
     @Override