Addressing MarlinFirmware#7552

When M405 is used it changes 'volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]' value. When M406 disables M405 it leaves the value unchanged.
This PR applies 'calculate_volumetric_multipliers' in M406 instead of resetting it to 1.0 because M200 may not be compatible with M405 hence I'm sure to restore anyway with correct value.

Marlin/Marlin_main.cpp

@@ -9241,7 +9241,10 @@ inline void gcode_M400() { stepper.synchronize(); }
   /**
    * M406: Turn off filament sensor for control
    */
-  inline void gcode_M406() { filament_sensor = false; }
+  inline void gcode_M406() {
+    filament_sensor = false;
+    calculate_volumetric_multipliers();   // Restore correct 'volumetric_multiplier' value
+  }
 
   /**
    * M407: Get measured filament diameter on serial output