motorBike tutorial - wrong viscosity in transportProperties

Typo in version 1706 as well as devel branch.

case: $FOAM_TUTORIALS/incompressible/simpleFoam/motorBike

Probably after cleaning constant/transportProperties file, the viscosity reads: .5e-5 instead of 1.5e-5. Unless we want motorBike to run across the air frozen to 170 Deg, it needs to be changed to 1.5e-5.