[NumPy] Replace numpy.asscalar(x) with x.item() in preparation for up…

…grading NumPy to 1.23.

NumPy 1.23 removes numpy.asscalar() (https://numpy.org/doc/stable/release/1.23.0-notes.html#expired-deprecations), which has been deprecated since NumPy 1.16 (https://numpy.org/doc/stable/release/1.16.0-notes.html#new-deprecations).

x.item() should be identical to the previous implementation of numpy.asscalar(x) in every way.

PiperOrigin-RevId: 466151898

trax/tf_numpy/numpy_impl/arrays.py

@@ -209,7 +209,7 @@ def __index__(self):
       ValueError: If the array does not have size 1.
     """
     # TODO(wangpeng): Handle graph mode
-    return np.asscalar(self.data.numpy())
+    return self.data.numpy().item()
 
   def tolist(self):
     return self.data.numpy().tolist()