Style: Replace header guards with #pragma once

modules/regex/tests/test_regex.h

@@ -28,8 +28,7 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
 /**************************************************************************/
 
-#ifndef TEST_REGEX_H
-#define TEST_REGEX_H
+#pragma once
 
 #include "../regex.h"
 
@@ -423,5 +422,3 @@ TEST_CASE("[RegEx] Lookbehind groups empty matches") {
 }
 
 } // namespace TestRegEx
-
-#endif // TEST_REGEX_H