Documentation bugfix of invalid JSON payload example of Create a commit with multiple files and actions

What does this MR do?

This MR removes a trailing comma from the payload example.

Why was this MR needed?

The comma makes JSON payload example invalid.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• 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?

I didn't create any.