ci(python): install Go in the Python client job so the SonarCloud scan runs on develop again

[devin-ai-integration]

What and why

The CircleCI "Python client tests" job has failed on every develop commit since make scripts-coverage started running scripts/mkdocs_suite_figures-test.py: its test_real_tree_renders_into_the_real_page renders the figures with go run ./cmd/doc-counts -site-blocks, and the cimg/python executor has no Go toolchain (FileNotFoundError: 'go'). Because the "SonarCloud scan" job requires that job, no analysis of develop has been published since, and the branch's quality gate is stuck on stale results.

This installs Go 1.25.0 in the python-test job through the circleci/go orb, the same way the Rust client job already does, so the scripts coverage run can render the figures and the scan runs again.

How it was verified

• The config parses as YAML; the added steps mirror the existing go/install + "Verify Go version" steps of rust-test.
• CI on this PR runs the modified job.

Checklist

• make test and make lint pass locally (n/a: CI config only)
• Tests added or updated for the change (n/a)
• Documentation extended where it already covers the surface (n/a)
• Changelog entry added (n/a: CI only)
• baselines regenerated (n/a)
• No internal work-item labels in the body, docs, or changelog

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[devin-ai-integration]

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