Replace a motion-sensor/timer with simple single pole switch
Switches that do something more than just "switch", often require neutral - timers, sensors, smart switches, etc. Ordinary switches do not require neutral. You actually have the opposite of the usual problem - someone who needs neutral but doesn't have it because it was not always required to be available. So your problem is easy to fix!


Cap the neutral


This is the simplest solution. If you had only one neutral in the box then that would be the thing to do - cap it with a wire nut and a piece of electrical tape to keep it secure since wire nuts do not always hold well with a single wire.


Remove the neutral.


If your neutral, as is often the case and appears to be the case in your box, goes to a bunch of other neutrals on a wire nut, remove the neutral wire from the wire nut and replace the wire nut. Or better, put on a new, appropriately sized, wire nut, to hold all the other neutral wires together, as reusing old wire nuts is iffy at best.