Few-Shot Relationship Extraction Example Error

While using the [spacy_llm rel_openai](https://github.com/explosion/spacy-llm/tree/main/usage_examples/rel_openai) example I continually run into the error:

- `IndexError: [E035] Error creating span with start 9 and end -1 for Doc of length 16.`

This error seems to only happen when providing the pipeline with an examples jsonl file for the few-shot learner to inference with. I tracked the issue down to [spacy_llm/tasks/rel/util:L58](https://github.com/explosion/spacy-llm/blob/main/spacy_llm/tasks/rel/util.py#L58) where the function "to_doc" appears to add the token index -1 for the end character I believe.

I do not understand why this error is occurring can someone please check in on this? I have also went ahead and attached the examples file I used as well as the stack trace of the error. The examples.json file extension was changed to json in order to upload to github. The real extension is .jsonl

[few_shot_trace.txt](https://github.com/explosion/spacy-llm/files/15027136/few_shot_trace.txt)
[examples.json](https://github.com/explosion/spacy-llm/files/15027141/examples.json)