pytest: Don't raise FutureWarning to Error

Otherwise we can't use this experimental feature.

.github/workflows/test_examples.yml

@@ -57,4 +57,4 @@ jobs:
         pip install .[test]
         pip install -U git+https://github.com/projectmesa/mesa@main#egg=mesa
     - name: Test with pytest
-      run: pytest -rA -Werror test_examples.py
+      run: pytest -rA -Werror -Wdefault::FutureWarning test_examples.py