ModelicaTest.MultiBody.Forces.DifferentiationOfForces was defined slightly differently as in MSL 3.2 (when removing an Obsolete model component). Fixed this by using exactly the same definition, in order
that regression testing does not report "validation failed"

git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@6414 7ce873d0-865f-4ce7-a662-4bb36ea78beb