`nbdev_conda` not honoring the license choice

The license is unconditionally set to "Apache" at the moment; see `_get_conda_meta` in https://github.com/fastai/nbdev/blob/master/nbs/api/release.ipynb

Should it be changed to take in `cfg.get('license')`, and the `license_family` field dropped?
conda-build will deduct the license family from the name if it's not specified.

On a related note, conda-forge requires that we set the `license_file`
https://github.com/conda-forge/staged-recipes/blob/main/.github/pull_request_template.md

https://docs.conda.io/projects/conda-build/en/latest/resources/define-metadata.html#license-file

If there is no reason against it, Is it safe to hard-code it to be just `LICENSE`? It's picked up from PyPI automatically.