Add pyyaml for management of docker-compose yaml files

[deverickapollo]

Summary This PR adds the python3-yaml package as a dependency in UmbrelOS. The addition of this package is necessary to manage Docker-Compose YAML files effectively within UmbrelOS.

Changes Added python3-yaml to the list of essential system utilities installed during the OS build process. Removed duplicate installs of python3.

Reasoning The python3-yaml package is required for parsing and managing YAML files, which are commonly used for Docker-Compose configurations. By including this package, we ensure UmbrelOS can handle Docker-Compose YAML files out of the box, improving the overall functionality and app developer experience.

Testing ❌ Built UmbrelOS with the updated Dockerfile. ❌ Verified that python3-yaml is installed and functional. ✅ Tested Docker-Compose YAML file management to ensure compatibility and functionality.

Notes No breaking changes are introduced with this PR. The addition of python3-yaml is backward-compatible and should not affect existing functionality.