Fix English special symbols (#12529)

Marlin/src/lcd/language/language_en.h

@@ -28,7 +28,6 @@
  * See also http://marlinfw.org/docs/development/lcd_language.html
  *
  */
-#define THIS_LANGUAGES_SPECIAL_SYMBOLS        _UxGT("³")
 
 #define en 1234
 #if LCD_LANGUAGE == en
@@ -36,6 +35,10 @@
 #endif
 #undef en
 
+#ifndef THIS_LANGUAGES_SPECIAL_SYMBOLS
+  #define THIS_LANGUAGES_SPECIAL_SYMBOLS      _UxGT("³")
+#endif
+
 #ifdef NOT_EXTENDED_ISO10646_1_5X7
   #define MSG_CUBED                           _UxGT("^3")
 #else