From a practical standpoint, you leave it alone. You're paying tax to Vandalia, on your total income, for the year, and that's good enough.
If you did not work in an any other individual city more than 20 days, you also meet the technical-legal requirement. Even if you didn't, the responsibility falls on your employer to do the proper withholding, not you.
You don't mention where you live. You normally only have to
file a return in the city you live in. It is not necessary to file one in the
city you work in, if different. Your employer will remit withholding to the
city you work in, but you do not file a return unless you're claiming a refund or
your employer didn't withhold enough ( both highly unusual). The city you live
in will allow a credit or partial credit for the withheld tax you paid to the
work location city.
