Update bigquery.md

[cipick]

Amplitude Developer Docs PR

Description

Describe your changes.

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

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[LeontiBrechko]

Hello @cipick,

Thanks for your contribution to keeping the docs in sync!

Could you elaborate a bit more on why you believe iam.serviceAccounts.getAccessToken is the required permission for BQ export, please? If you have an Amplitude customer ticket open, a link to it would be helpful to understand the context better