collab: Drop legacy subscription usage and meter tables (#29876)

Marshall Bowers created

This PR adds a migration to drop the `subscription_usages` and
`subscription_usage_meters` tables from the database.

We're now using `subscription_usages_v2` and
`subscription_usage_meters_v2` everywhere.

Release Notes:

- N/A

Change summary

crates/collab/migrations_llm/20250504132836_drop_legacy_subscription_usage_and_meter_tables.sql | 2 
1 file changed, 2 insertions(+)

Detailed changes