Is the switch for this light actually inside your unit? If so you would have control over this light and presumably be paying the bill for it. Even though it is on a walkway, if you have the control and not the OC, I would think you would be responsible for changing the light bulb.
I have a light outside my front door, on the wall which is common property. The switch is inside my place. Though I can’t change this light, or remove it without permission, I have never thought of it as anything but my responsibility to change the light bulb.