Avoid listing org packages where job token doesn't have access

[mering]

This allows using the job token directly.

Example workflow:

permissions:
  packages: write

jobs:
  cleanup-images:
    runs-on: ubuntu-22.04
    steps:
      - name: Cleanup untagged images
        uses: mering/delete-untagged-ghcr-action@main
        with:
          token: ${{ github.token }}
          repository_owner: ${{ github.repository_owner }}
          repository: ${{ github.repository }}
          package_name: IMAGE_NAME
          untagged_only: true
          owner_type: org