Set minimal python version to 3.11

[romanc]

Description

PyFV3 requires a minimum python version 3.11. This was updated two months ago. This commit cleans up the following two leftovers:

1. In setup.py, update the classifiers
2. In the Dockerfile, start from the python 3.11 image

How Has This Been Tested?

Tested by running make build locally. Before this change, the command would fail (because of the numpy and pyFV3's setup.py dependency to python >= 3.11). With this change, I can build the docker image and run savepoint tests.

Note: running make savepoint_tests fails before and after this change with the same error summary.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas: N/A
• I have made corresponding changes to the documentation: N/A
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules: N/A
• New check tests, if applicable, are included: N/A
• Targeted model if this changed was triggered by a model need/shortcoming: N/A

[romanc]

@FlorianDeconinck can you please review (once you are back tomorrow)?

[FlorianDeconinck]

@mlee03 This (slightly) touches the Docker file in pyFV3 that you might be using for CI

[FlorianDeconinck]

LGTM