Update JWT Login Docs to include Unified Access Token, and and fix PAT table formatting

[rubywerman]

In December 2025, we added UAT, a new JWT-based auth type for Tableau Cloud: https://help.tableau.com/current/api/cloud-manager/en-us/docs/unified_access_tokens.html

@BereketBirbo added UAT to the TSC library here: https://github.com/tableau/server-client-python/pulls?q=is%3Apr+author%3ABereketBirbo+is%3Aclosed., which has been merged into the development branch.

This MR updates the docs to show the new parameter, and fixed a formatting issue on the PAT section (the table wasn't showing up)
Before:

After:

JWT updates:

[salesforce-cla]

Thanks for the contribution! It looks like @ruby-sf is an internal user so signing the CLA is not required. However, we need to confirm this.