Enforce numpy v1.x

Code generation trips over repr(np.float64(1)) != 1.0 in numpy 2.0.
Properly fixing this would require to bump a lot of dependencies,
which is currently out of scope.

python/setup.py

@@ -51,6 +51,7 @@ setup(name='dune.codegen',
                         'cerberus',
                         'pyaml',
                         'clang-format',
+                        'numpy<2',
                         ],
       cmdclass={'test': PyTest},
       entry_points = {