Cleanup two occurances of removed scheduler

[EwoutH]

Follow-up on the removal of the schedulers, removes a mention in the Model docstring and one check in the DataCollector.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
BoltzmannWealth	small	🟢 -7.3% [-8.8%, -5.8%]	🔵 -0.2% [-0.3%, -0.0%]
BoltzmannWealth	large	🔵 -1.9% [-2.5%, -1.5%]	🟢 -6.9% [-7.6%, -6.3%]
Schelling	small	🔵 -2.3% [-2.6%, -2.0%]	🔵 -0.9% [-1.1%, -0.7%]
Schelling	large	🔵 -0.5% [-1.0%, +0.0%]	🟢 -3.7% [-4.4%, -3.0%]
WolfSheep	small	🔵 -1.7% [-1.9%, -1.5%]	🔵 -0.9% [-1.0%, -0.7%]
WolfSheep	large	🔵 -2.3% [-2.8%, -1.7%]	🟢 -5.4% [-7.3%, -3.6%]
BoidFlockers	small	🔵 +0.4% [-0.2%, +0.9%]	🔵 +0.6% [-0.1%, +1.3%]
BoidFlockers	large	🔵 +1.0% [+0.6%, +1.5%]	🔵 +0.5% [-0.3%, +1.3%]