message: Add migration block for tf.compat.v1.placeholder
diff: @@ -3251,10 +3251,6 @@ def placeholder(dtype, shape=None, name=None):
  print(sess.run(y, feed_dict={x: rand_array})) # Will succeed.
  ```
  - @compatibility(eager)
  - Placeholders are not compatible with eager execution.
  - @end_compatibility
  -
  Args:
  dtype: The type of elements in the tensor to be fed.
  shape: The shape of the tensor to be fed (optional). If the shape is not
  @@ -3267,6 +3263,20 @@ def placeholder(dtype, shape=None, name=None):
  Raises:
  RuntimeError: if eager execution is enabled
  +
  + @compatibility(TF2)
  + This API is not compatible with eager execution and `tf.function`. To migrate
  + to TF2, rewrite the code to be compatible with eager execution. Check the
  + [migration
  + guide](https://www.tensorflow.org/guide/migrate#1_replace_v1sessionrun_calls)
  + on replacing `Session.run` calls. In TF2, you can just pass tensors directly
  + into ops and layers. If you want to explicitly set up your inputs, also see
  + [Keras functional API](https://www.tensorflow.org/guide/keras/functional) on
  + how to use `tf.keras.Input` to replace `tf.compat.v1.placeholder`.
  + `tf.function` arguments also do the job of `tf.compat.v1.placeholder`.
  + For more details please read [Better
  + performance with tf.function](https://www.tensorflow.org/guide/function).
  + @end_compatibility
  """
  if context.executing_eagerly():
  raise RuntimeError("tf.placeholder() is not compatible with "
  