cleanup: Switch to pragma once

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3157>

clutter/clutter/clutter-shader-types.h

@@ -21,8 +21,7 @@
  * License along with this library. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef __CLUTTER_SHADER_TYPES_H__
-#define __CLUTTER_SHADER_TYPES_H__
+#pragma once
 
 #if !defined(__CLUTTER_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
 #error "Only <clutter/clutter.h> can be included directly."
@@ -94,5 +93,3 @@ const gfloat *  clutter_value_get_shader_matrix (const GValue *value,
                                                  gsize        *length);
 
 G_END_DECLS
-
-#endif /* __CLUTTER_SHADER_TYPES_H__ */