Allow receiver to unshare another instructor's question pool

Receiver of a shared pool (pool owned by other person) would like to be able to remove the share when they are done with it.

• Instructor 1 shares a question pool with Instructor 2
• Instructor 2 copied all questions from pool
• Instructor 2 would like to no longer see the shared pool
  Currently instructor 2 must contact instructor 1 to unshare the pool, would prefer if Instructor 2 could remove the share.

UI suggestion in ticket https://jira.sakaiproject.org/browse/SAM-1567