Intro course: Revise the course to use the new PDF generator

### Description

We should no longer encourage new users to stick with the old PDF generator. It still needs to be enabled using a feature flag, but we should have them do this as part of the intro course. It is also much easier to work with the new generator, and we should encourage them to use the PDF preview in the developer tools to get the PDF looking how they want.

### Additional Information

_No response_

Start at the intro course content and locate the current instructions for the old PDF generator. Update the course to cover enabling the new generator with its feature flag and using PDF preview in developer tools; done means new users are no longer directed to the old generator.

Written by the indexing model from the issue text.