Set migration completed to false

What does this MR do and why?

Fixing the flaky spec #468741 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Add set_elasticsearch_migration_to :create_work_items_index, including: true in the spec
2. Run the spec you will see the same errors.