Resolve "Remove unused unique indexes related to SBOM tables"

What does this MR do and why?

Drop unique indexes for the sbom_* tables that are no longer used. They've been replaced with new unique indexes that include organization_id (sharding key). The new indexes were introduced in 17.3, which is an upgrade stop.

• 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.

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Related to #479190 (closed)