Apply #pragma once, misc cleanup (#12322)

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

Marlin/src/lcd/language/language_en.h

@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  *
  */
+#pragma once
 
 /**
  * English
@@ -27,8 +28,6 @@
  * See also http://marlinfw.org/docs/development/lcd_language.html
  *
  */
-#ifndef LANGUAGE_EN_H
-#define LANGUAGE_EN_H
 
 #define en 1234
 #if LCD_LANGUAGE == en
@@ -1149,5 +1148,3 @@
     #define MSG_FILAMENT_CHANGE_RESUME_1        _UxGT("Resuming...")
   #endif
 #endif // LCD_HEIGHT < 4
-
-#endif // LANGUAGE_EN_H