By law, you do not need it, assume you did not even file it.
However, if you do get requested for it you still fine because tax docs will not have info about how long you worked just how much you made. For all it matter is could have been an oncampus work as well which does not require work permit.
Unauthorised work is considered permissible or I would say ignored if its less than 180 days for 485 application.

I say you are fine. Don't submit things that you dont have to.