[gnome-clocks] timer-setup-dialog: Call Gtk.Box.append() instead of Gtk.Box.add()

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit d70b41bf4a20cd1dc7befc14036cae6d372ab4ff
Author: Yetizone <andreii lisita gmail com>
Date:   Mon Mar 1 19:14:45 2021 +0200

    timer-setup-dialog: Call Gtk.Box.append() instead of Gtk.Box.add()
    
    Gtk.Box.add() is no longer available in GTK4

 src/timer-setup-dialog.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/timer-setup-dialog.vala b/src/timer-setup-dialog.vala
index e360ad85..f4adfe37 100644
--- a/src/timer-setup-dialog.vala
+++ b/src/timer-setup-dialog.vala
@@ -32,7 +32,7 @@ public class SetupDialog: Gtk.Dialog {
         create_button.get_style_context ().add_class ("suggested-action");
 
         timer_setup = new Setup ();
-        this.get_content_area ().add (timer_setup);
+        this.get_content_area ().append (timer_setup);
         timer_setup.duration_changed.connect ((duration) => {
             this.set_response_sensitive (Gtk.ResponseType.ACCEPT, duration != 0);
         });