v3.33.2

Changes

• #1572 Fix #1571 initial_value for RichTextInputElement should also accept type RichTextBlock - Thanks @macintacos @seratch
• #1574 Switch canvases.* APIs to application/json format for more stability - Thanks @seratch

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• All issues/pull requests: https://github.com/slackapi/python-slack-sdk/milestone/105?closed=1
• All changes: https://github.com/slackapi/python-slack-sdk/compare/v3.33.1...v3.33.2