📝 Update DISABLE_INACTIVE_* comment

Followup to MarlinFirmware#25422

Author: thinkyhead

Marlin/Configuration_adv.h

@@ -1118,7 +1118,7 @@
 
 /**
  * Idle Stepper Shutdown
- * Set DISABLE_INACTIVE_? 'true' to shut down axis steppers after an idle period.
+ * Enable DISABLE_INACTIVE_* to shut down axis steppers after an idle period.
  * The Deactive Time can be overridden with M18 and M84. Set to 0 for No Timeout.
  */
 #define DEFAULT_STEPPER_DEACTIVE_TIME 120