Update cli_helpers dependency to v2.15.1

[rolandwalker]

Description

Update cli_helpers dependency to v2.15.1, which contains a minor robustness bugfix, in case of passing explicit but empty headers

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the AUTHORS file (or it's already there).
• To lint and format the code, I ran

  uv run ruff check && uv run ruff format && uv run mypy --install-types .