Update Docker base image to Ubuntu 22.04 LTS by Madhumn123 · Pull Request #1295 · sqlancer/sqlancer

This PR updates the Docker base image from Ubuntu 21.04 (which is End-of-Life)
to Ubuntu 22.04 LTS.

Ubuntu 21.04 no longer receives security updates, which may expose the image
to vulnerabilities. Upgrading to Ubuntu 22.04 LTS ensures long-term support,
improved stability, and continued security patches.

No other changes were made to the Docker configuration.