AMP-84981 updated TradeDesk cohort sync docs

[yunishimura0716]

Amplitude Developer Docs PR

Description

• updated the part of user mapping
• updated the part of consideration (with explanation of Time-to-Live parameter)

Deadline

When do these changes need to be live on the site?

Change type

• Doc bug fix. Fixes #[insert issue number]. Amplitude contributors include Jira issue number.
• Doc update.
• New documentation.
• Non-documentation related fix or update.

PR checklist:

• My documentation follows the style guidelines of this project.
• I previewed my documentation on a local server using mkdocs serve.
• Running mkdocs serve didn't generate any failures.
• I have performed a self-review of my own documentation.

@amplitude-dev-docs

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ MARKDOWN	markdownlint	1		0	0.26s

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