Remove invalid option extruder

[LongDono]

extruder is a valid option for filament_motion_sensor, but not for filament_switch_sensor

Option 'extruder' is not valid in section 'filament_switch_sensor runout_sensor'

Once the underlying issue is corrected, use the "RESTART"
command to reload the config and restart the host software.
Printer is halted

[Frix-x]

Oh, good catch. I'm not using one myself so didn't see this error. I'll merge to the develop branch for the next release :)

[LongDono]

Happy to help but I'm new to this... Hence my deleting the branch while on mobile and then restoring it thinking that was a mistake. On the desktop, I can see it says it was safe to delete. Thank you for all your work on Klippain!