Bump gh-aw-firewall to v0.28.16 and gh-aw-mcpg to v0.4.21

Update the bundled dependency versions to:

- [`github/gh-aw-firewall` v0.28.16](https://github.com/github/gh-aw-firewall/releases/tag/v0.28.16)
- [`github/gh-aw-mcpg` v0.4.21](https://github.com/github/gh-aw-mcpg/releases/tag/v0.4.21)

Ensure generated files and dependency references are updated consistently.