Stop checking migration version in project factory

What does this MR do?

Since we've truncated the migrations after 2018-12-28 (see db/migrate/20181228175414_init_schema.rb) we can safely remove this check which reduces the query count for a project factory by 1.

Related to &3752

Also contributes to https://gitlab.com/gitlab-org/plan/-/issues/145.

Queries saved: 55463 overall. See !40098 (comment 400412711)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
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