Change keyboard level include guards to pragma once (#14248)

* Change keyboard level include guards to `pragma once`

And clean up a lot of layout macros

* Oops

* Remove dangling endif

keyboards/mechmini/v2/config.h

@@ -12,8 +12,8 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
-#ifndef V2_CONFIG_H
-#define V2_CONFIG_H
+
+#pragma once
 
 #include "config_common.h"
 
@@ -62,5 +62,3 @@
 #define RGBLIGHT_SAT_STEP 8
 #define RGBLIGHT_VAL_STEP 8
 #endif
-
-#endif