ENH: tutorial script: rm was producing an error if folder was not presnt

tutorials/incompressible/pimpleDyMFoam/propeller/Allclean

@@ -7,6 +7,6 @@ cd ${0%/*} || exit 1    # run from this directory
 cleanCase
 
 \rm -rf 0
-\rm -r constant/extendedFeatureEdgeMesh/
+\rm -rf constant/extendedFeatureEdgeMesh/
 \rm -f constant/triSurface/*.eMesh*