Replace a few more deprecated numpy aliases of builtin types

See https://numpy.org/devdocs/release/1.20.0-notes.html#deprecations

PiperOrigin-RevId: 414674669
Change-Id: I74847aac15d815458a3974baa26d1c8683d3f4df

Author: alimuldal

dm_env/specs.py

@@ -170,7 +170,7 @@ class BoundedArray(Array):
   integer types. The following spec will be satisfied by arrays
   with values in the set {0, 1, 2}:
   ```python
-  spec = BoundedArray((3, 4), np.int, minimum=0, maximum=2)
+  spec = BoundedArray((3, 4), int, minimum=0, maximum=2)
   ```
 
   Note that one or both bounds may be infinite. For example, the set of

dm_env/specs_test.py

@@ -300,7 +300,7 @@ def testGenerateValue(self):
     spec.validate(test_value)
 
   def testScalarBounds(self):
-    spec = specs.BoundedArray((), np.float, minimum=0.0, maximum=1.0)
+    spec = specs.BoundedArray((), float, minimum=0.0, maximum=1.0)
 
     self.assertIsInstance(spec.minimum, np.ndarray)
     self.assertIsInstance(spec.maximum, np.ndarray)