chore(main): release 9.15.0

[github-actions]

🤖 I have created a release beep boop

9.15.0 (2026-01-07)

Features

• Drop support for python 3.9 (#393) (5b761bd)

Bug Fixes

• Add context manager for clearer, safer locks (#396) (beca0fa)
• Address potential race condition in FeatureStore update_availability (#391) (31cf487)
• Stop FeatureStoreClientWrapper poller on close (#397) (468afdf)

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Note

Release 9.15.0

• Documents dropping support for Python 3.9 and lists bug fixes (lock context manager, race condition in FeatureStore.update_availability, stop FeatureStoreClientWrapper poller on close) in CHANGELOG.md
• Bumps version to 9.15.0 in pyproject.toml, ldclient/version.py, .release-please-manifest.json, and updates SDK_VERSION in PROVENANCE.md

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