In football, is there a difference between an overhead kick and a scissor kick?

No. If you read this web page, scissors kick and overhead kick are just different names for the bicycle kick.

https://en.wikipedia.org/wiki/Bicycle_kick

As golden says one in the same. If you do a search in google under scissor kick - wikipedia it refers you to Bicycle kick, a move in football.

https://en.wikipedia.org/wiki/Scissor_kick

Yes there is a difference. Wikipedia is not always right ppl. Most players do overhead kick rather than scissor kick (bicycle kick). If you jump with your right foot and contact the ball with right foot to shoot that is overhead kick. On the other hand scissor kick/bicycle kick is when you jump with your right foot and switch the leg in the air to kick with left foot. Only bicycle kick that I know of is from pele.
Most people doesn't know this and just call it scissor kick/bicycle kick where they kick above the head.