Fix axis string 'N' (MarlinFirmware#24259)

Followup to 167672d

Author: kisslorand

Marlin/src/core/serial.cpp

@@ -35,7 +35,7 @@ PGMSTR(SP_P_STR, " P"); PGMSTR(SP_T_STR, " T"); PGMSTR(NUL_STR,   "");
 
 #define _N_STR(N) PGMSTR(N##_STR, STR_##N);
 #define _N_LBL(N) PGMSTR(N##_LBL, STR_##N ":");
-#define _SP_N_STR(N) PGMSTR(SP_##N##_STR, STR_##N ":");
+#define _SP_N_STR(N) PGMSTR(SP_##N##_STR, " " STR_##N);
 #define _SP_N_LBL(N) PGMSTR(SP_##N##_LBL, " " STR_##N ":");
 MAP(_N_STR, LOGICAL_AXIS_NAMES); MAP(_SP_N_STR, LOGICAL_AXIS_NAMES);
 MAP(_N_LBL, LOGICAL_AXIS_NAMES); MAP(_SP_N_LBL, LOGICAL_AXIS_NAMES);