Fix display of the group identified in the nested groups table

Steps to reproduce:

1. Go to Administration > Users & groups
2. Click the New button then select Group
3. Create a first group with
   • identifier = subgroupId
   • label = Subgroup Label
4. Create a second group with
   • identifier = maingroupId
   • label = Main Group Label
   • members = subgroupId
5. Go back to Administration > Users & groups
6. Search for "maingroupId"
7. In the results, click on the group "maingroupId"
8. Observe in the table "Nested groups" that the group label "Subgroup Label" is displayed in the column "identifier"

Expected behavior: the group id is displayed in the column "identifier