Fix to runout sensor code. (#12431)

- "old_state" is no longer a class static variable.

Marlin/src/feature/runout.cpp

 }
 
 #if ENABLED(FILAMENT_MOTION_SENSOR)
-  uint8_t FilamentSensorEncoder::motion_detected,
-          FilamentSensorEncoder::old_state; // = 0
+  uint8_t FilamentSensorEncoder::motion_detected;
 #endif
 
 #if FILAMENT_RUNOUT_DISTANCE_MM > 0