Fix Chiron probe low point (#19962)

Marlin/src/lcd/extui/lib/anycubic_chiron/chiron_tft_defs.h

@@ -54,7 +54,7 @@
 #define MAX_PATH_LEN                   16 * MAX_FOLDER_DEPTH // Maximum number of characters in a SD file path
 
 #define AC_HEATER_FAULT_VALIDATION_TIME 5    // number of 1/2 second loops before signalling a heater fault
-#define AC_LOWEST_MESHPOINT_VAL        -7.00 // The lowest value you can set for a single mesh point offset
+#define AC_LOWEST_MESHPOINT_VAL        Z_PROBE_LOW_POINT // The lowest value you can set for a single mesh point offset
 
  // TFT panel commands
 #define  AC_msg_sd_card_inserted       PSTR("J00")