Clean up apt-get lists after every apt package installation

[PeterDaveHello]

It's somehow missing in some steps.

Summary from GitHub Copilot:

This pull request optimizes the Dockerfile by improving image cleanliness and reducing its size. The changes ensure that temporary files created during package installation are removed to minimize the image's footprint.

Dockerfile optimizations:

• Added rm -rf /var/lib/apt/lists/* after installing pipx to clean up temporary files and reduce image size. ([DockerfileR95](https://github.com/openai/codex-universal/pull/1/files#diff-dd2c0eb6ea5cfc6c4bd4eac30934e2d5746747af48fef6da689e85b752f39557R95))
• Added rm -rf /var/lib/apt/lists/* after installing ruby-full to remove unnecessary files and maintain a clean image. ([DockerfileL176-R178](https://github.com/openai/codex-universal/pull/1/files#diff-dd2c0eb6ea5cfc6c4bd4eac30934e2d5746747af48fef6da689e85b752f39557L176-R178))

[PeterDaveHello]

@joshma-openai #3 & #4 should further improve the Dockerfile and Docker image. Please feel free to let me know if there's anything else I can do for it;)

[joshma-openai]

Hey @PeterDaveHello thank you for the PRs! We're a bit behind on things but will get to them in the next week or so, sorry in advance.