Fix "possible buffer overrun" warning (#17513)

Marlin/src/lcd/menu/menu_ubl.cpp

@@ -188,8 +188,8 @@ void _lcd_ubl_edit_mesh() {
  */
 void _lcd_ubl_validate_custom_mesh() {
   char ubl_lcd_gcode[24];
-  const int temp = TERN(HAS_HEATED_BED, custom_bed_temp, 0);
-  sprintf_P(ubl_lcd_gcode, PSTR("G28\nG26 C B%i H%i P"), temp, custom_hotend_temp);
+  const int16_t temp = TERN(HAS_HEATED_BED, custom_bed_temp, 0);
+  sprintf_P(ubl_lcd_gcode, PSTR("G28\nG26 C B%" PRIi16 " H%" PRIi16 " P"), temp, custom_hotend_temp);
   queue.inject(ubl_lcd_gcode);
 }