chore: move serde-yaml to dev dependencies

Summarize the changes

Previous version was using yaml-rust which is marked as unmaintained. This gets reported by dependency scanner we use for certification. Though worth noting that serde-yaml itself is now archived. There is a promising replacement library but no need to hurry with that just yet. But anyway, we don't need this library in the production build, only for tests. So, moved it to development dependencies.

Ensure that

• New code is covered by unit and integration tests.
• Related issues would be automatically closed with gitlab's closing pattern (Closes #1, #2).
• Public modules are documented (check the rendered version with cargo doc --open).
• (if PEST grammar is changed) EBNF grammar reflects these changes (check the result with railroad diagram generator.

Next steps

• Cherry-pick to: none
• Update sbroad submodule in picodata/picodata.
• (if EBNF grammar is changed) create a follow-up issue in picodata/docs.