Drop Support for EOL Python 3.6, 3.7 and 3.8

As of today per Python Software Foundation policy here: https://devguide.python.org/versions/

• Python 3.6 has ended security support and it's end of life was - 2021-12-23. It's 3 years unsupported!
• Python 3.7 has ended security support and it's end of life was - 2023-06-27. It's 1.5 years unsupported!
• Python 3.8 has ended security support and it's end of life was - 2024-10-07. It's 3 months unsupported!

Does Slack SDK plans to remove support for those Python versions? Promoting unsupported version of Python has security concerns and it shouldn't be promoted.

I've realised this while working on #1633 as I wasn't expecting that Python 3.6 is in use and I was using features that were added in Python 3.8 so I lived under assumption that I can use everything from 3.9 and above.

Category

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.models (UI component builders)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.scim (SCIM API client)
• slack_sdk.rtm (RTM client)
• slack_sdk.signature (Request Signature Verifier)

Requirements

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Không có tệp, bài kiểm thử hoặc điểm vào nào được nêu. Hãy bắt đầu bằng việc xem xét cấu hình dự án và các tham chiếu CI đến những phiên bản Python được hỗ trợ, sau đó kiểm tra các thành phần SDK được liệt kê để xác định khả năng hỗ trợ theo từng phiên bản. Công việc được xem là hoàn tất khi Python 3.6, 3.7 và 3.8 không còn được hỗ trợ một cách nhất quán trên các thành phần đó và phần xác thực liên quan đã được cập nhật.