✏️ 9-axis followup (sanity-check)

Marlin/src/inc/Conditionals_LCD.h

@@ -669,9 +669,9 @@
  * Number of Linear Axes (e.g., XYZIJKUVW)
  * All the logical axes except for the tool (E) axis
  */
-#ifdef LINEAR_AXES
-  #undef LINEAR_AXES
-  #define LINEAR_AXES_WARNING 1
+#ifdef NUM_AXES
+  #undef NUM_AXES
+  #define NUM_AXES_WARNING 1
 #endif
 
 #ifdef W_DRIVER_TYPE

Marlin/src/inc/SanityCheck.h

@@ -619,6 +619,8 @@
   #error "Z_STEPPER_ALIGN_KNOWN_STEPPER_POSITIONS is now just Z_STEPPER_ALIGN_STEPPER_XY."
 #elif defined(DWIN_CREALITY_LCD_ENHANCED)
   #error "DWIN_CREALITY_LCD_ENHANCED is now DWIN_LCD_PROUI."
+#elif defined(LINEAR_AXES)
+  #error "LINEAR_AXES is now NUM_AXES (to account for rotational axes)."
 #elif defined(X_DUAL_STEPPER_DRIVERS)
   #error "X_DUAL_STEPPER_DRIVERS is no longer needed and should be removed."
 #elif defined(Y_DUAL_STEPPER_DRIVERS)