fix release-docs workflow credentials

[tamirkamara]

Change Description

mkdocs needs credentials to push to the pages branch. One method is to persist the GitHub token from the checkout step (which we remove everywhere else).

Checklist

• I have reviewed the contribution guidelines
• I have signed the CLA (if required)
• My code includes unit tests
• All unit tests and lint checks pass locally
• My PR contains documentation updates / additions if required