Remove out of ref image bounds check for planar figures
Summary: I couldn't identify any error in vtkPolyDataToImageStencil anymore as stated in a code comment.
Test Plan: Manual testing. I couldn't create an open planar figure that is out of image bounds for testing, though. Only circle, ellipse, and double ellipse.
Reviewers: O1 MITK Reviewer Group I, floca
Reviewed By: O1 MITK Reviewer Group I, floca
Maniphest Tasks: T26508
Differential Revision: https://phabricator.mitk.org/D268