Settings: Fix queryShortcuts_shouldOnlyIncludeSystemApp test

Previously this test asserted that the ActivityInfo instances
were the same address. While this can assert general equality,
it is more robust to assert the ActivityInfo's properties-
mainly that the associated application is a system app.

Bug: b/314924127
Test: atest SettingsRoboTests:com.android.settings.shortcut.CreateShortcutPreferenceControllerTest
Flag: TEST_ONLY
Change-Id: I0d60fb848afdd40cecf3f3393421006ad1ff1086