docs: fix broken example image paths in output_files docs

[yzxcj797]

The layout/span example images in docs/en/reference/output_files.md and docs/zh/reference/output_files.md are referenced as ../images/layout_example.png and ../images/spans_example.png, which resolve to docs/en/images/ and docs/zh/images/ - directories that do not exist. The images live in the shared docs/images/ directory, so the correct relative path is ../../images/.... The rendered docs currently show broken images.

[github-actions]

Thank you for your submission, we really appreciate it. Like many open-source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution. You can sign the CLA by just posting a Pull Request Comment same as the below format.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}