Revert "Add the settings content observer for shortcut preference."

This reverts commit 785af0c15a.

Bug: 155837154

Reason for revert: robolectric test fail at com.android.settings.accessibility.ToggleFeaturePreferenceFragmentTest

Change-Id: If8e5681b044171ad6941307489526cc3834f66b2

src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java

@@ -467,8 +467,7 @@ public class ToggleScreenMagnificationPreferenceFragment extends
         showDialog(DialogEnums.MAGNIFICATION_EDIT_SHORTCUT);
     }
 
-    @Override
-    protected void updateShortcutPreferenceData() {
+    private void updateShortcutPreferenceData() {
         // Get the user shortcut type from settings provider.
         mUserShortcutType = getUserShortcutTypeFromSettings(getPrefContext());
         if (mUserShortcutType != UserShortcutType.EMPTY) {
@@ -490,8 +489,7 @@ public class ToggleScreenMagnificationPreferenceFragment extends
         mShortcutPreference.setTitle(title);
     }
 
-    @Override
-    protected void updateShortcutPreference() {
+    private void updateShortcutPreference() {
         final int shortcutTypes = getUserShortcutTypes(getPrefContext(), UserShortcutType.SOFTWARE);
         mShortcutPreference.setChecked(
                 hasMagnificationValuesInSettings(getPrefContext(), shortcutTypes));