Updated Mounted Squires unit card

Add new units: Mounted Squires!
Royal Mounted Yeomen and Royal Mounted Yeomen Archers are brought down a tier each.

Upkeep reduction further reduced to -20% for melee infantry units, down from -25%

NOTE: Autonomous collective Tech was buffed, this nerf was made to offset that extra change. The start of the campaign is likely harder now than it was a week ago, but easier than it was before the addition of the upkeep reduction.

Added a new effect, making the Upkeep reduction for peasants only effect melee infantry

-30% upkeep bonus reduced to -25%