Remove unnecessary custom libyaml

[deivid-rodriguez]

What are you trying to accomplish?

As per #7112 (review), current ubuntu version ships a modern enough libyaml-dev, so I think #7112 can be mostly revert.

Anything you want to highlight for special attention from reviewers?

I did keep making psych an explicit dependency from #7112, because I believe it's used directly by Dependabot.

How will you know you've accomplished your goal?

CI is good I guess!

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.