[PR #14256/8638c7d3 backport][9.0.x] docs: clarify reportinfo() return tuple in non-python example

[patchback]

This is a backport of PR #14256 as merged into main (8638c7d).

Summary

• Clarify the expected return value of reportinfo() in the non-Python collection example.
• Document the tuple structure as (path, lineno, description).
• Explain each element (path, zero-based lineno, and description) in plain language.

Closes #6689

Notes

• Documentation-only change; no runtime behavior changed.
• Tests are not required for this docs clarification.