Fix editing names of account-level groups

Fixes CNVS-14996

Test plan:
  - Create an account-level group
  - Edit said group's name
  - Ensure that when you hit "save", the dialog goes away, and the group's
    name updates accordingly

Change-Id: Ie6be56e9481a08fe5dc16a6dca7a627523b02511
Reviewed-on: https://gerrit.instructure.com/40384
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brad Horrocks <bhorrocks@instructure.com>
Reviewed-by: Joel Hough <joel@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>