BREAKING Fixed ContourElementTest

Summary:
T28464 introduced changes to ContourElement insert behavior.
Instead of silently dropping outofbound
inserts, it now behaves like stl vector::insert.
Thus inserts outofbound will be inserted at
the end. Test had to be adapted accordingly.

Test Plan: code review, test should be green

Reviewers: O3 MITK Reviewer Group II, kislinsk

Reviewed By: O3 MITK Reviewer Group II, kislinsk

Differential Revision: https://phabricator.mitk.org/D698