message: doctest update decimal precision
diff: @@ -1871,7 +1871,7 @@ def rgb_to_grayscale(images, name=None):
  >>> original = tf.constant([[[1.0, 2.0, 3.0]]])
  >>> converted = tf.image.rgb_to_grayscale(original)
  >>> print(converted.numpy())
  - [[[1.8149]]]
  + [[[1.81...]]]
  ```
  