[SPARK-59184][BUILD] Cleanup remaining references to Python 3.10 or earlier

[nchammas]

What changes were proposed in this pull request?

1. Update remaining requirements of Python 3.10+ to instead require Python 3.11+.
2. Drop stale environment variables specifying Python 3.9.

Why are the changes needed?

1. These seem to be an oversight vs. a deliberate choice. Spark requires Python 3.11 or newer. I don't see a reason to allow 3.10 anywhere.
2. The docs job overrides the Python 3.9 env vars with Python 3.12 in a later step. It's confusing to have both specified in the same job when only the latter is what's intended.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

CI

Was this patch authored or co-authored using generative AI tooling?

No.

[dongjoon-hyun]

If you don't mind, please file a new JIRA issue for this, @nchammas .

[nchammas]

OK done. For the future, could you elaborate on why this needs a new ticket vs. a follow-up to the existing one?

[dongjoon-hyun]

OK done. For the future, could you elaborate on why this needs a new ticket vs. a follow-up to the existing one?

Let me ask you why you think removing Python 3.9-leftover is related to SPARK-56889 (Drop Python 3.10 Support), @nchammas ?

[nchammas]

Let me ask you why you think removing Python 3.9-leftover is related to SPARK-56889 (Drop Python 3.10 Support), @nchammas ?

That's a minor drive-by cleanup that is topically related. I didn't think it was a big deal to include.