Update tpu_strategy.py

rank[DEP] -> ndim
diff --git a/tensorflow/python/distribute/tpu_strategy.py b/tensorflow/python/distribute/tpu_strategy.py
index b574c52..a8ffa61 100644
--- a/tensorflow/python/distribute/tpu_strategy.py
+++ b/tensorflow/python/distribute/tpu_strategy.py
@@ -897,7 +897,7 @@
           if tensor_util.is_tensor(input_tensor):
             rank = input_tensor.get_shape().rank
           else:
-            rank = np.rank(input_tensor)
+            rank = np.ndim(input_tensor)
           maximum_shape = tensor_shape.TensorShape([None] * rank)
           maximum_shapes.append(maximum_shape)
         maximum_shapes = nest.pack_sequence_as(replicate_inputs[0],