py versions

[martindurant]

py3.14 is definitely stable by now, and 3.9 is no longer maintained. The aproproate pyproject fields and CI job configs should be updated.
This is not urgent!

Cf fsspec/filesystem_spec#1946

[kyleknap]

This makes sense to me! Azure SDK is also dropping 3.9 in April: https://github.com/Azure/azure-sdk-for-python/wiki/Azure-SDKs-Python-version-support-policy and the SDK is tested on 3.14 so there is alignment there. We can look into this more next week!