Set default fanspeed for monotonic ironing to -1
Set default fanspeed for monotonic ironing to -1

Since it was set to 100 by default, it would always turn the fan on fully.
This was probalby missed during the first tests, as most of the default settings
have the fanspeed at 100.

CURA-8567
Fixes Ultimaker/Cura#10407

Ultimaker/CuraEngine,Ultimaker/CuraEngine