scrolledwindow: Don't take adjustments in new()

In 99.9% of all cases, these are just NULL, NULL.
So just do away with these arguments, people can
use the setters for the rare cases where they want
the scrolled window to use a different adjustment.

demos/print-editor/print-editor.c

@@ -768,7 +768,7 @@ activate (GApplication *app)
   gtk_window_set_child (GTK_WINDOW (main_window), box);
 
   /* Create document  */
-  sw = gtk_scrolled_window_new (NULL, NULL);
+  sw = gtk_scrolled_window_new ();
 
   gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (sw),
                                   GTK_POLICY_AUTOMATIC,