Missed a couple more #pragma onces (#11351)

tests/test_common/test_matrix.h

@@ -14,8 +14,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef TESTS_TEST_COMMON_TEST_MATRIX_H_
-#define TESTS_TEST_COMMON_TEST_MATRIX_H_
+#pragma once
 
 #ifdef __cplusplus
 extern "C" {
@@ -28,5 +27,3 @@ void clear_all_keys(void);
 #ifdef __cplusplus
 }
 #endif
-
-#endif /* TESTS_TEST_COMMON_TEST_MATRIX_H_ */