remove _advance_time() from benchmark model

Now automatically

Author: EwoutH

benchmarks/BoltzmannWealth/boltzmann_wealth.py

@@ -38,7 +38,6 @@ def __init__(self, seed=None, n=100, width=10, height=10):
         self.datacollector.collect(self)
 
     def step(self):
-        self._advance_time()
         self.agents.shuffle().do("step")
         # collect data
         self.datacollector.collect(self)