Add missing dependency to tracing docs (#6421)

## Why are these changes needed?

Add missing dependency to tracing docs

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solves. -->

## Related issue number

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Closes #6419

## Checks

- [ ] I've included any doc changes needed for
<https://microsoft.github.io/autogen/>. See
<https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md> to
build and test documentation locally.
- [ ] I've added tests (if relevant) corresponding to the changes
introduced in this PR.
- [ ] I've made sure all auto checks have passed.