flocking benchmark: Remove unneeded passing of pos

pos is not a part of the Boid init, which is causing an error. It can be safely removed, because it's already initialized the line below with `self.space.place_agent(boid, pos)`

Author: EwoutH

benchmarks/Flocking/flocking.py

@@ -139,7 +139,6 @@ def __init__(
             boid = Boid(
                 unique_id=i,
                 model=self,
-                pos=pos,
                 speed=speed,
                 direction=direction,
                 vision=vision,