Allow any format for X-Request-Id

# Prerequisites

Please answer the following questions for yourself before submitting an issue.

- [x] I am running the latest code. Development is very rapid so there are no tagged versions as of now.
- [x] I carefully followed the [README.md](https://github.com/abetlen/llama-cpp-python/blob/main/README.md).
- [x] I [searched using keywords relevant to my issue](https://docs.github.com/en/issues/tracking-your-work-with-issues/filtering-and-searching-issues-and-pull-requests) to make sure that I am creating a new issue that is not already open (or closed).
- [x] I reviewed the [Discussions](https://github.com/abetlen/llama-cpp-python/discussions), and have a new bug or useful enhancement to share.

# Expected Behavior

Normal response (200)

# Current Behavior

400, Bad request

# Environment and Context
Huggingface spaces docker

# Failure Information (for bugs)
Feature introduced in https://github.com/abetlen/llama-cpp-python/pull/703, Huggingface Spaces already has `x-request-id` in the request, but it was not a valid uuid that `starlette-context` expected (https://github.com/tomwojcik/starlette-context/blob/992ab9401a9f557994379053fbd98471c601eda9/tests/test_plugins/test_request_id.py#L37), resulting in the server returning bad request 400.