Remove ignore column rules for shared_runners_duration

What does this MR do and why?

Remove ignore column rules for shared_runners_duration

• Ci::Minutes::ProjectMonthlyUsage
• Ci::Minutes::NamespaceMonthlyUsage

See https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#migrating-integer-primary-keys-to-bigint

• backfill is done (in 16.4) at !129573 (merged)
• column swap is done (in 16.5) at !132225 (merged)
• cleanup is done (in 16.6) at !134037 (merged)

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Related to #424826 (closed)