feedstock repo: move python specification from meta.yaml

from [a suggestion](https://github.com/conda-forge/genomekit-feedstock/pull/91#issuecomment-5114629270) by the automated conda-forge linter bot:

For **recipe/meta.yaml**:

* ℹ️ top-level output overrides versions pinned in the feedstock:
['- In section host: `python python`']
Requirement spec should not list version specifiers to respect conda-forge-pinning. If you need to force another version, please override the pin via `conda_build_config.yaml`.

Start with recipe/meta.yaml and inspect the host requirements where Python is specified. Compare the recipe with the conda-forge linter suggestion and check conda_build_config.yaml only if a pin override is needed. Done means the recipe no longer overrides the feedstock's Python version pin.

Written by the indexing model from the issue text.