[gnome-control-center] sound: Replace ifdefs with #pragma once

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 667fe61e7851e9ee061c58f31d64b5368a35e14e
Author: Robert Ancell <robert ancell canonical com>
Date:   Thu Nov 21 20:41:31 2019 +1300

    sound: Replace ifdefs with #pragma once

 panels/sound/gvc-mixer-stream-private.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/panels/sound/gvc-mixer-stream-private.h b/panels/sound/gvc-mixer-stream-private.h
index c5aacd77d..e9b155270 100644
--- a/panels/sound/gvc-mixer-stream-private.h
+++ b/panels/sound/gvc-mixer-stream-private.h
@@ -17,8 +17,7 @@
  *
  */
 
-#ifndef __GVC_MIXER_STREAM_PRIVATE_H
-#define __GVC_MIXER_STREAM_PRIVATE_H
+#pragma once
 
 #include <glib-object.h>
 
@@ -29,5 +28,3 @@ G_BEGIN_DECLS
 pa_context *        gvc_mixer_stream_get_pa_context  (GvcMixerStream *stream);
 
 G_END_DECLS
-
-#endif /* __GVC_MIXER_STREAM_PRIVATE_H */