Apply #pragma once, misc cleanup (#12322)

* Apply #pragma once in headers
* Adjust some thermistors formatting
* Misc cleanup and formatting

Marlin/src/module/temperature.h

@@ -19,14 +19,12 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
+#pragma once
 
 /**
  * temperature.h - temperature controller
  */
 
-#ifndef TEMPERATURE_H
-#define TEMPERATURE_H
-
 #include "thermistor/thermistors.h"
 #include "../inc/MarlinConfig.h"
 
@@ -660,5 +658,3 @@ class Temperature {
 };
 
 extern Temperature thermalManager;
-
-#endif // TEMPERATURE_H