Duplicate contract entries in Airtable causes failing test in `dim_contract_attachments`

[cal-itp-sentry[bot]]

As a Cal-ITP data user, I don't want duplicate data in the warehouse so that I can be sure that my joins won't cause fanout. Specifically, we don't want duplicate rows in the dim_contract_attachments table.

Sentry Issue: CAL-ITP-DATA-INFRA-15ZY

DbtTestFail: test.calitp_warehouse.dbt_utils_mutually_exclusive_ranges_dim_contract_attachments_required___valid_from__source_record_id___valid_to.acdbe74ec9 - Got 2 results, configured to fail if != 0

[lauriemerrell]

This is an issue with the raw Airtable data, there are duplicate entries: https://cal-itp.slack.com/archives/C040XD9UB33/p1683322012914689