[SofaPython] removing an unnecessary dynamic_cast
[SofaPython] removing an unnecessary dynamic_cast

(cherry picked from commit 3bf248ccad6c1b9ae1d8d3ab3ba24f72f56add2a)

FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa,FabienPean/sofa