Follow-up from "Allow bulk update for group issues - milestones"

The following discussion from !14141 (merged) should be addressed:

• @dbalexandre started a discussion: (+6 comments)

  My concern is that someone can change the ids in issuable_ids and we apply these changes to issues that do not belong to the group/project. I think that is fine to leave this as is and open a follow-up issue to check. WDYT?