Remove dataset list in README

[jeanpaulrsoucy]

The data explorer at Covid19CanadaArchive-data-explorer has reached feature parity with the one in the README of this repository. The README-based dataset list can be removed.

• [ ] Remove generate_readme function from utils.py
• [ ] Remove GitHub Actions workflow (.github/workflows/update-readme.yml)
• [ ] Convert to static README (remove docs/README_content.md)
• [ ] Update entry for dataset explorer in README