The solution is to change the name of the group in Constituent360 before changing the name of your TeamRaiser.
  1. Navigate to Constituent360 > select Groups
  2. In the search field, type in the new TeamRaiser name that you were attempting to use when the error was produced
  3. You should see a group name in the following naming convention: TeamRaiser Name Donors
  4. Click Edit for the Donors group
  5. Type a new name for the group and click Save
  6. Attempt to change the name of your TeamRaiser again