Revert the mercy hps buff

[Ryan-111758]

@BuLTT-1848

Why does hero get so much value by just merely clicking in the general direction direction of a teammate.

@GeoffGoodman

Mercy is intended to be able to consistently pump out more healing than any other healer over the course of a match.

@GeoffGoodman

which she pays for by not being able to split focus and do other things while healing.

Avg damage per game: 302