feat: update GAPIC samples to be featured in create message guide

[PierrickVoulet]

Description

Porting edits based on golden googleworkspace/python-samples#1690.

Is it been tested?

• Development testing done

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have performed a peer-reviewed with team member(s)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules

[snippet-bot]

Here is the summary of changes.

You are about to delete 1 region tag.

• chat/advanced-service/Main.gs:108, tag chat_create_message_app_cred_with_cards

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