Fix CommitDetails entity to use using keyword

What does this MR do and why?

• Fix CommitDetails entity to use using keyword.
  • Grape Entities should use using: when declaring nested entities, rather than documentation.type.
• There are no user-facing changes here, except the documentation will now be more accurate.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.