[docs-agent] Clean up Docs Agent's README.md files.

[kyolee415]

Description of the change

Clean up Docs Agent's README.md files.

Motivation

Clean up Docs Agent's README.md files.

Type of change

Choose one: (Documentation)

Checklist

• [ X] I have performed a self-review of my code.
• [ X] I have added detailed comments to my code where applicable.
• [ X] I have verified that my change does not break existing code.
• [ X] My PR is based on the latest changes of the main branch (if unsure, please run git pull --rebase upstream main).
• [ X] I am familiar with the Google Style Guide for the language I have coded in.
• [ X] I have read through the Contributing Guide and signed the Contributor License Agreement.