[gtk/a11y/atspi] Fixup: Add a forgotten #pragma once

[Matthias Clasen <matthiasc src gnome org>]

commit d6b64b5e291f7515e8fd4d272a48b5deea7a89d8
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Oct 10 13:43:48 2020 -0400

    Fixup: Add a forgotten #pragma once

 gtk/a11y/gtkatspiutilsprivate.h | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/gtk/a11y/gtkatspiutilsprivate.h b/gtk/a11y/gtkatspiutilsprivate.h
index 6d4f661026..dc8be1cca8 100644
--- a/gtk/a11y/gtkatspiutilsprivate.h
+++ b/gtk/a11y/gtkatspiutilsprivate.h
@@ -18,6 +18,8 @@
  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#pragma once
+
 #include "gtkatspiprivate.h"
 #include "gtkenums.h"