Add exact pin (#4945)

Author: kratman

pyproject.toml

@@ -31,7 +31,7 @@ dependencies = [
     "pybammsolvers",
     "numpy>=1.23.5,<2.0.0",
     "scipy>=1.11.4",
-    "casadi>=3.6.7,<3.7.0",
+    "casadi==3.6.7",
     "xarray>=2022.6.0",
     "anytree>=2.8.0",
     "sympy>=1.12",