Remove "show-in" action

Summary: Remove "show-in" action from the data manager view

Test Plan:
manual UI testing
(for this to work the mxnmultiwidget-plugin has to be activated)

• open MITK, load an image
• select the node and open the context menu
• the menu entry "Show in" is not available

Reviewers: floca, O1 MITK Reviewer Group I

Reviewed By: floca, O1 MITK Reviewer Group I

Subscribers: kalali, kislinsk, floca

Maniphest Tasks: T25725

Differential Revision: https://phabricator.mitk.org/D658