[WIP] Revert changes from commit 106134b in Azure SDK for Python

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Revert commit 106134b4e2f0da13f6b759dc6002635aaa693cad in Azure/azure-sdk-for-python.

The commit message is Align Agent Server Core with 2.2.0 beta. It is the current head commit of pull request #48753 and has parent cc08e0cb6193d0c10078dbf307aa3c598e328fe6. Create a clean revert commit/PR against main that restores exactly the three changes introduced by that commit:

1. In sdk/agentserver/azure-ai-agentserver-core/CHANGELOG.md, change the unreleased heading from ## 2.2.0b1 (Unreleased) back to ## 2.1.1 (Unreleased).
2. In sdk/agentserver/azure-ai-agentserver-core/azure/ai/agentserver/core/_version.py, change VERSION = "2.2.0b1" back to VERSION = "2.1.1".
3. In sdk/agentserver/azure-ai-agentserver-core/pyproject.toml, change the classifier from Development Status :: 4 - Beta back to Development Status :: 5 - Production/Stable.

Do not revert any other changes from the pull request or surrounding commits. Run focused validation if available, and report the resulting commit and pull request.

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