Mobs from mob spawners spawn on minecart rails as well as redstone wire.

Steps to Reproduce:

1. Place mob spawner
2. Use a zombie spawn egg on it
3. Surround the floor around the spawner with rails, or redstone wire

Expected: Mobs will not spawn
Observed: Mobs do spawn either on top of the block (if there is not enough room to spawn above it in the air) or will spawn directly on the rail.

Relates to MC-92609