[MM-61071] Fix errcheck issues in channels/app/admin.go (#28756)

server/.golangci.yml

@@ -85,7 +85,6 @@ issues:
         channels/api4/team_test.go|\
         channels/api4/user_test.go|\
         channels/api4/webhook_test.go|\
-        channels/app/admin.go|\
         channels/app/app_test.go|\
         channels/app/authorization_test.go|\
         channels/app/auto_responder_test.go|\