Is it possible to speed up the way mob spawners spawn mobs?
Solution 1:
If you set up a command block on a Redstone clock with /tp ~ 1 ~ you can teleport the villagers to a different area which speeds up the spawn rate as there won't be as many villagers in one place.
Solution 2:
I don't believe that there is any way to speed up the spawn rate of mob spawners.
Here's a link on how spawners work in case you want to check out their mechanics.
https://minecraft.gamepedia.com/Spawner#Mechanics