labeler.yml: Use settings from ggerganov/llama.cpp [no ci] (#7363)

https://github.com/actions/labeler#using-configuration-path-input-together-with-the-actionscheckout-action
Recommends the use of checkout action to use the correct repo context
when applying settings for PR labels

e.g.

    steps:
    - uses: actions/checkout@v4 # Uploads repository content to the runner
      with:
        repository: "owner/repositoryName" # The one of the available inputs, visit https://github.com/actions/checkout#readme to find more
    - uses: actions/labeler@v5
      with:
        configuration-path: 'path/to/the/uploaded/configuration/file'