Stabilize AgentSet

[EwoutH]

Removes the experimental warning for the AgentSet.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
Schelling	small	🔵 -0.7% [-1.0%, -0.4%]	🔵 -0.1% [-0.3%, +0.1%]
Schelling	large	🔵 -0.6% [-1.0%, -0.1%]	🔵 +0.3% [+0.0%, +0.6%]
WolfSheep	small	🔵 -0.2% [-0.8%, +0.5%]	🔵 -0.0% [-0.1%, +0.1%]
WolfSheep	large	🔵 -0.3% [-0.6%, -0.0%]	🔵 +0.6% [+0.1%, +1.1%]
BoidFlockers	small	🔵 +1.5% [+0.8%, +2.2%]	🔵 +1.4% [+0.7%, +2.0%]
BoidFlockers	large	🔵 +1.7% [+1.0%, +2.3%]	🔵 +0.1% [-0.7%, +0.8%]

[Corvince]

Thanks!