QoL improvements for Sym

[Ana-23891]

@Kyarameru-11252

Turrets no longer lock on Mei in cyro-freeze and DVa’s mech

It was sort of implemented for Torb after the rework by doing

@GeoffGoodman

Torbjörn’s turret will also now assist you by firing at enemies damaged by Rivet Gun’s primary fire, giving players some control over the AI targeting. Note: It will not attempt to target enemies not in its line of sight.

They could prob do something similar for Symm.