Document generation CI is broken (#13308)
### Description
<!-- Describe your changes. -->
Fix document generation CI. It's not currently updating the docs as
we're skipping the tests, which is the invocation of build.py that would
have generated the documentation.
Setup specific task to generate documentation for greater clarity.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Operator kernel documentation is not getting updated and is now out of
date.
