Revert partition of package metadata tables

What does this MR do and why?

Adds a migration that ensures that package metadata tables are not partitioned. This is needed to fix databases of environments where package metadata tables have been partitioned by !104155 (merged) (reverted) before !108644 (merged) was merged.

Here's the sequence:

• !104155 (merged) added a migration to partition pm_packages, pm_package_versions, and pm_package_version_licenses.
• The migration was deployed to staging, but not to production.
• !108644 (merged) removed that migration.
• This very MR is needed to revert the changes in the DB schema of staging.

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How to set up and validate locally

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MR acceptance checklist

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Related to #382567