fix(NewUserDialog): update group selection to prevent admin group from being assigned as subadmin

Signed-off-by: Arsalan Ul Haq Sohni <arsalan-ul-haq.sohni@strato.de>

[skip ci]

Author: Arsalanulhaq

apps/settings/src/components/Users/NewUserDialog.vue

@@ -218,6 +218,10 @@ export default {
 			return groups.filter(group => group.id !== '__nc_internal_recent' && group.id !== 'disabled')
 		},
 
+		availableSubAdminGroups() {
+			return this.availableGroups.filter((group) => group.id !== 'admin')
+		},
+
 		languages() {
 			return [
 				{