Fix typo in documentation
Fix typo in documentation

The variable name is _dest_point, it seems.

Contributes to issue CURA-2229.

ROBO3D/CuraEngine,ROBO3D/CuraEngine,ROBO3D/CuraEngine,alephobjects/CuraEngine,Ultimaker/CuraEngine,Ultimaker/CuraEngine,alephobjects/CuraEngine,alephobjects/CuraEngine