message: Update core.py
  fix typo in deprecation warning
diff: @@ -112,7 +112,7 @@ class Dense(keras_layers.Dense, base.Layer):
  @deprecation.deprecated(
  date=None,
  - instructions='Use keras.layers.dense instead.')
  + instructions='Use keras.layers.Dense instead.')
  @tf_export(v1=['layers.dense'])
  def dense(
  inputs, units,
  