[gnome-contacts] window: Disambiguate Gtk.HeaderBar

[Niels De Graef <nielsdg src gnome org>]

commit c5eee38cd2556403a640a0a4c11d36cbf9a5a798
Author: Niels De Graef <nielsdegraef gmail com>
Date:   Thu May 30 14:30:54 2019 +0200

    window: Disambiguate Gtk.HeaderBar
    
    Apparently libhandy also added a HeaderBar type, which means this
    clashes with that of Gtk.

 src/contacts-window.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/contacts-window.vala b/src/contacts-window.vala
index 738228d..49f6995 100644
--- a/src/contacts-window.vala
+++ b/src/contacts-window.vala
@@ -35,9 +35,9 @@ public class Contacts.Window : Gtk.ApplicationWindow {
   [GtkChild]
   private TitleBar titlebar;
   [GtkChild]
-  private HeaderBar left_header;
+  private Gtk.HeaderBar left_header;
   [GtkChild]
-  private HeaderBar right_header;
+  private Gtk.HeaderBar right_header;
   [GtkChild]
   private Overlay notification_overlay;
   [GtkChild]