Add MAPPER_C2C3 to French language

Marlin/language_fr.h

@@ -30,6 +30,7 @@
 #ifndef LANGUAGE_FR_H
 #define LANGUAGE_FR_H
 
+#define MAPPER_C2C3
 #define DISPLAY_CHARSET_ISO10646_1
 
 #define WELCOME_MSG                         MACHINE_NAME _UxGT(" prête.")