Remove flag for checkRemoteViewsUris

This change removes the
android.appwidget.flags.check_remote_views_uri_permission flag. This is
required for security fixes (see bug comment #55).

Bug: 369137473
Test: atest "CtsAppWidgetTestCases:AppWidgetTest#testCheckRemoteViewsUri"
Flag: EXEMPT security fix
Change-Id: Ie83f78c6efe878dabe7a422bf6ca497f31761005