Add timezone property to slack_sdk.models.TimePickerElement class

[seratch]

While Node and Java SDKs already have the new property, this Python SDK still does not have the newly added timezone property in the TimePickerElement.

We are still waiting for the document updates here but we can add the property with some general description (we can update it once the API documents are ready).

See also:

• Add timezone property to Timepicker block element node-slack-sdk#1502
• Added in timezone string property to timepicker block element in types package node-slack-sdk#1503
• Add timezone property to timepicker block element java-slack-sdk#1010

Category (place an x in each of the [ ])

• 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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[seratch]

Fixed by #1251