[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: 656014404
Change-Id: I289f3fa71acf50a3df4d393ed8394a48181527db

tf_agents/specs/tensor_spec_test.py

@@ -444,7 +444,7 @@ def testFromSpec(self):
       self.assertEqual(expected_spec, spec)
 
   def testFromStringSpec(self):
-    spec = tensor_spec.from_spec(array_spec.ArraySpec([1], np.string_))
+    spec = tensor_spec.from_spec(array_spec.ArraySpec([1], np.bytes_))
     self.assertEqual(tf.string, spec.dtype)