Issue in vision api document text detection example

[mfarberbrodsky]

In which file did you encounter the issue?

https://github.com/GoogleCloudPlatform/python-docs-samples/blob/master/vision/cloud-client/document_text/doctext.py

Did you change the file? If so, how?

No.

Describe the issue

Here are lines 88, 89 of this file:

        if (feature == FeatureType.PAGE):
            bounds.append(block.bounding_box)

Here, in case the feature requested is the page - the block's bounding box is added, instead of the page's. This needs to be changed to page.bounding_box.

[nnegrey]

@busunkim96, has a fix in this PR #2705.

Page doesn't actually have a bounding_box field, so we'll remove that from the tutorial.
https://cloud.google.com/vision/docs/reference/rpc/google.cloud.vision.v1#google.cloud.vision.v1.Page