DOC: Minor update for 'Surfaces'

Hi,

In https://openfoam.com/documentation/cpp-guide/html/guide-fos-sampling-surfaces.html ,

pimpleDyMFoam propeller tutorial: $FOAM_TUTORIALS/incompressible/pimpleDyMFoam/propeller

might need to be updated to:

pimpleFoam propeller tutorial: $FOAM_TUTORIALS/incompressible/pimpleFoam/RAS/propeller

Kind regards