In the case where a review request that had file attachments also had

the Asana or Trello integration fields active, the event overlay on the

file attachment would be on top of the dropdown. This overlay is

invisible, so it was just catching events meant for thee dropdown.

This change adds some CSS rules to put those at the correct z-index.

Added a file attachment and verified that I could now select items in

the Asana and Trello dropdown menus that happened to be at the same

coordinates as the file attachment.