Incorrect pdf count

[AgaDufrat]

Raised via Zendesk:

• https://govuk.zendesk.com/agent/tickets/5877929
• https://govuk.zendesk.com/agent/tickets/6231061
• https://govuk.zendesk.com/agent/tickets/6252809

Fix incorrect pdf count, which appears to happen after re-importing the data from GA4 in Content Data API.

This appears to be a source of issues as Facts::Metric are created from publishing events (via RabbitMQ)

content-data-api/app/domain/etl/main/main_processor.rb

Line 17 in dff14d5

delete_existing_metrics if already_run?

Why

This feature is used to audit where inaccessible PDF content exists. Departments struggle to remove accessibility debt without it.