misc/codex: Update to 0.120.0

Changelog:

• https://github.com/openai/codex/releases/tag/rust-v0.118.0
• https://github.com/openai/codex/releases/tag/rust-v0.119.0
• https://github.com/openai/codex/releases/tag/rust-v0.120.0

Reported by: GitHub (watch releases)