Removing unsupported getEmailMetadata method and adding modify method

[alwestmo-openai]

Summary

This PR updates the gpt_action_gmail.ipynb file to reflect changes in the Gmail API integration. Specifically:
• Removed the no longer supported getEmailMetadata method from the OpenAPI schema.
• Added the modify method to enable programmatic modification of email labels.
These changes ensure the guide aligns with the current capabilities of the Gmail API and supports relevant use cases for developers.

Motivation

The getEmailMetadata method is deprecated and no longer supported by the Gmail API, which could cause confusion or errors for developers. Replacing it with the modify method addresses this gap by providing functionality for modifying email labels, a feature commonly used in workflows for email organization and management.

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[aaronwilkowitz-openai]

LGTM!