errcheck issues fixed (#28693)

server/.golangci.yml

@@ -93,7 +93,6 @@ issues:
         channels/api4/system_test.go|\
         channels/api4/team_local.go|\
         channels/api4/team_test.go|\
-        channels/api4/upload_test.go|\
         channels/api4/user.go|\
         channels/api4/user_local.go|\
         channels/api4/user_test.go|\