unpin poetry

A new minor version of poetry (2.3) was just [released](https://python-poetry.org/blog/announcing-poetry-2.3.0/) two days ago, which raises an error when installed in github actions. I've pinned poetry to 2.2 in the [initial PR](https://github.com/pacificclimate/ncpartitioner/pull/3), but it should be unpinned when things stabilize around the new version.