Revert "Refactor BiometricEnrollBase::onStop()"

This reverts commit 6b6d8c0d6d.

Reason for revert: Should use shouldFinishWhenBackgrounded() to
control the behavior during onStop()

Bug: 197717071
Change-Id: I6aeacd5fb0d4400911a2e3d1567db660a0f1798a

src/com/android/settings/biometrics/BiometricEnrollIntroduction.java

@@ -241,16 +241,6 @@ public abstract class BiometricEnrollIntroduction extends BiometricEnrollBase
         }
     }
 
-    @Override
-    protected void onStop() {
-        if (!isChangingConfigurations() && shouldFinishWhenBackgrounded()
-                && !BiometricUtils.isAnyMultiBiometricFlow(this)) {
-            setResult(RESULT_TIMEOUT);
-            finish();
-        }
-        super.onStop();
-    }
-
     @Override
     protected void onSaveInstanceState(Bundle outState) {
         super.onSaveInstanceState(outState);