Fix todos API endpoint application error

What does this MR do?

Handles correctly target_type "Commit" for Todo Entity in api.

Why was this MR needed?

To avoid 500 error when todos include todo that has generated by a reference in a commit.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #22951 (closed)