To remove the shared topic from the group it was shared to, you can go to settings and unpublish or expire the topic.

To expire the topic, you will go to the group you want the topic removed from:
  1. Edit the Topic
  2. Click the cogwheel on the left hand side
  3. Edit Settings
  4. At the bottom of the screen, put in an expire date for the group you don't want it published to
  5. Save