CD updater: add missing call in tests

ag/31885242 changed the behavior for registerCallback such that it no
longer automatically scheduled an update. This CL adds the missing call
in tests.

Flag: com.android.settings.flags.display_topology_pane_in_display_list
Test: atest ExternalDisplayUpdaterTest.java
Test: atest ConnectedDeviceGroupControllerTest.java
Bug: b/399273324
Change-Id: If030e7cc98289fe3062c1a638580ec6c6479d97a

tests/unit/src/com/android/settings/connecteddevice/display/ExternalDisplayUpdaterTest.java

@@ -63,6 +63,7 @@ public class ExternalDisplayUpdaterTest extends ExternalDisplayTestBase {
             return null;
         }).when(mMockedCallback).onDeviceAdded(any());
         mUpdater.initPreference(mContext, mMockedInjector);
+        mUpdater.refreshPreference();
         mUpdater.registerCallback();
         mHandler.flush();
         assertThat(mPreferenceAdded).isNotNull();
@@ -85,6 +86,7 @@ public class ExternalDisplayUpdaterTest extends ExternalDisplayTestBase {
             return null;
         }).when(mMockedCallback).onDeviceRemoved(any());
         mUpdater.initPreference(mContext, mMockedInjector);
+        mUpdater.refreshPreference();
         mUpdater.registerCallback();
         mHandler.flush();
         assertThat(mPreferenceAdded).isNotNull();