[numpy] Fix users of NumPy APIs that are removed in NumPy 2.0.

This change migrates users of APIs removed in NumPy 2.0 to their recommended replacements (https://numpy.org/devdocs/numpy_2_0_migration_guide.html).

PiperOrigin-RevId: 656738213

pybind11_abseil/tests/absl_test.py

@@ -377,7 +377,7 @@ def test_fill_span_from_numpy(self):
       ('read_only', make_read_only_numpy_array()),
       ('strided_skip', make_strided_numpy_array(2)),
       ('strided_reverse', make_strided_numpy_array(-1)),
-      ('non_supported_type', np.zeros(5, dtype=np.unicode_)),
+      ('non_supported_type', np.zeros(5, dtype=np.str_)),
       ('native_list', [0] * 5))
   def test_fill_span_fails_from(self, values):
     with self.assertRaises(TypeError):