Remove unused unique indexes related to SBOM tables

Why are we doing this work?

Per backwards compatibility docs, migrations run before new code gets deployed. This means that any schema migrations we make need to be compatible with the old code. For this reason, while creating new unique indexes to sbom_ tables with the new column organization_id, in some cases we did not remove the old unique index (i.e. the one w/o organization_id). These old unique indexes need to be removed.

See (size: L) Govern: Threat Insights - Cells Support (&13087 - closed)

Further details

The following MRs introduced new unique DB indexes that include the organization_id column, used as a sharding key.

• Add org to `sbom_source_packages` (!159026 - merged)
• Add org to sbom_components (!161288 - merged)

These new DB indexes are normal DB migrations, and they're part of 17.3.

17.3 is an upgrade stop.

Implementation plan

• Drop idx_sbom_source_packages_on_name_and_purl_type, replaced by index_sbom_source_packages_on_name_and_purl_type_and_org_id.
• Drop index_sbom_components_on_component_type_name_and_purl_type, replaced by idx_sbom_components_on_name_purl_type_component_type_and_org_id.
• Drop index_sbom_component_versions_on_component_id_and_version. See #469435 (comment 2092272041)