Remove output from changing livewire points

Summary: I noticed a stray std::cout in the livewire code that quickly spams the console whenever a point is moved when editing the contour. I would assume it can just be removed.

Test Plan: Create a contour using the livewire tool (with auto-confirm turned off) and move one of the control points around. There should be no more position output in the console log.

Reviewers: O1 MITK Reviewer Group I, floca

Reviewed By: O1 MITK Reviewer Group I, floca

Differential Revision: https://phabricator.mitk.org/D724