message: add usage example to reduce_min
diff: @@ -2222,6 +2222,11 @@ def reduce_min(input_tensor, axis=None, keepdims=False, name=None):
  Returns:
  The reduced tensor.
  + For example:
  + >>> a = tf.constant([[1, 2], [3, 4]])
  + >>> tf.reduce_min(a)
  + <tf.Tensor: id=2, shape=(), dtype=int32, numpy=1>
  +
  @compatibility(numpy)
  Equivalent to np.min
  @end_compatibility
  