chore(deps): update dependency notifications-python-client to v9

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
notifications-python-client	==8.2.0 -> ==9.0.0

Review

• Updates have been tested and work
• If updates are AWS related, versions match the infrastructure (e.g. Lambda runtime, database, etc.)

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Release Notes

alphagov/notifications-python-client (notifications-python-client)

v9.0.0

Compare Source

• Removes the is_csv parameter to prepare_upload.
• Adds the filename parameter to prepare_upload. See our documentation for guidance on how to use this.

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