In general, no; rockets aren't equipped to pump propellant between stages. You load each stage with enough fuel to do its job, plus a safety margin, and if you discard leftover fuel you congratulate yourself for having built a system with reliable performance, and on future missions, you might load a little less propellant and/or take a little more payload!
In the specific case of the Apollo architecture, after the descent, there was known to be more than enough propellant in the LM ascent stage to do the ascent. If the ascent stage underperformed for some reason and launched into too low an orbit, the command/service module carried enough extra propellant to come and get it.
Building additional unused tankage capacity into the ascent stage, anticipating tapping some propellant from the descent stage, would have made the ascent stage bigger and heavier, and keeping the weight of the LM to a minimum was a major engineering challenge in the development of Apollo.
So in the end, the Apollo spacecraft either vented or abandoned propellant from the descent stage (on the moon), the ascent stage (after CSM/LM rendezvous), and the service module (before separation from the CM prior to reentry).
However, the LM ascent stage did have separate tankage for the small RCS thrusters, which used the same propellants as the ascent engine, and it was possible to pump between those tanks! According to Apollo By The Numbers, Apollo 9, 10, 11, and 12 transferred some ascent engine fuel (~20-45kg) to the RCS tanks, and 16 transferred some from the RCS tanks to the ascent tanks. The ascent engine could fire only once, and RCS was used to complete the rendezvous maneuvering with the CSM after ascent, so it makes sense that some unused fuel might be more useful in the RCS tanks at that point, but 130-190kg of propellants remained unused in the ascent tanks on all the landing missions.
As SF. reminds me, the propellant left in the descent stage could have been used by simply reigniting the descent stage when it was time to leave and beginning the ascent with that, then staging onto the ascent stage when descent fuel ran out. This would be a similar flight plan to the LM's abort-from-descent option. All it would accomplish would be saving more fuel to discard later in the mission.