[compatible] Config: run dune fmt in src/config

[dannywillems]

On top of dw/reformat-dune-files-src-test. See for the reasons of the atomicity: #16124

Explain your changes:
*

Explain how you tested your changes:
*

Checklist:

• Dependency versions are unchanged
  • Notify Velocity team if dependencies must change in CI
• Modified the current draft of release notes with details on what is completed or incomplete within this project
• Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• All tests pass (CI will check this if you didn't)
• Serialized types are in stable-versioned modules
• Does this close issues? List them

• Closes #0000

[dannywillems]

!ci-build-me

[dannywillems]

Closing for now. I would certainly open a new one in the future when I'll be back on Mina.