Same as PR #4293, just for Part as noted in https://github.com/FreeCAD/FreeCAD/pull/4271#discussion_r554673632 the pointer to the UI should be a unique pointer. This PR does this for all Part dialogs that don't already use a unique_ptr.
git-svn-id: https://free-cad.svn.sourceforge.net/svnroot/free-cad/trunk@5000 e8eeb9e2-ec13-0410-a4a9-efa5cf37419d