fix: Reverse dict key and value for agents_by_type

[rht]

This change is so that the agents_by_type API is compatible with Mesa 2.1.5 again.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
Schelling	small	🔵 +0.2% [-0.1%, +0.6%]	🔵 +0.1% [-0.0%, +0.3%]
Schelling	large	🔵 +1.1% [+0.8%, +1.5%]	🔴 +6.6% [+4.6%, +8.3%]
WolfSheep	small	🔵 +3.0% [+2.6%, +3.4%]	🔵 +0.6% [+0.5%, +0.8%]
WolfSheep	large	🔴 +10.1% [+5.0%, +14.4%]	🔴 +9.6% [+6.0%, +13.2%]
BoidFlockers	small	🔵 +1.7% [+1.4%, +2.1%]	🔵 +2.4% [+1.8%, +3.0%]
BoidFlockers	large	🔵 +1.3% [+0.8%, +1.7%]	🔵 +1.7% [+1.4%, +2.0%]

[quaquel]

Looks good to me, but you have 2 other changes here that are more ruff related. Do these belong within this PR?

[rht]

The other commits, when done in separate PR, will be ignored in the release note anyway. This PR can be rebase and merged, if the goal is not to mix lint changes into 1 commit.

[quaquel]

Fine with me either way.

[EwoutH]

Thanks!