version 3.27.2

Changes

• #1498 Fix #1496 Async client uses blocking call when uploading file with v2 - Thanks @kdrob @seratch
• #1492 Fix #1468 RichTextElement.elements items are never promoted to a proper Python object type - Thanks @k1e1n04 @kezabelle

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• All issues/pull requests: https://github.com/slackapi/python-slack-sdk/milestone/94?closed=1
• All changes: v3.27.1...v3.27.2