[gnome-control-center] display: Fix wrong widget type used

[Robert Ancell <rancell src gnome org>]

commit f00a5e20cb78ec7a6749666baf2d25d04d6eb03c
Author: Robert Ancell <robert ancell canonical com>
Date:   Wed Nov 20 12:42:25 2019 +1300

    display: Fix wrong widget type used

 panels/display/cc-display-panel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/panels/display/cc-display-panel.c b/panels/display/cc-display-panel.c
index 524793070..1b8184dcc 100644
--- a/panels/display/cc-display-panel.c
+++ b/panels/display/cc-display-panel.c
@@ -110,8 +110,8 @@ struct _CcDisplayPanel
   GtkComboBox    *output_selection_combo;
   GtkStack       *output_selection_stack;
   GtkButtonBox   *output_selection_two_buttonbox;
-  GtkButtonBox   *output_selection_two_first;
-  GtkButtonBox   *output_selection_two_second;
+  GtkRadioButton *output_selection_two_first;
+  GtkRadioButton *output_selection_two_second;
   HdyComboRow    *primary_display_row;
   GtkWidget      *stack_switcher;
 };