Added missing translations.

Marlin/language_es.h

 #define MSG_EXTRUDE                         "Extruir"
 #define MSG_RETRACT                         "Retraer"
 #define MSG_MOVE_AXIS                       "Mover ejes"
+#define MSG_LEVEL_BED                       "Nivelar cama"
 #define MSG_MOVE_X                          "Mover X"
 #define MSG_MOVE_Y                          "Mover Y"
 #define MSG_MOVE_Z                          "Mover Z"

Marlin/language_it.h

 #define MSG_EXTRUDE                         "Estrudi"
 #define MSG_RETRACT                         "Ritrai"
 #define MSG_MOVE_AXIS                       "Muovi Asse"
+#define MSG_LEVEL_BED                       "Livellamento piano"
 #define MSG_MOVE_X                          "Muovi X"
 #define MSG_MOVE_Y                          "Muovi Y"
 #define MSG_MOVE_Z                          "Muovi Z"