Move the spec for the Integration concern

What does this MR do?

This MR moves the spec for the Integration concern to where the spec should be, and will reduce the size of a diff for when we need to rename this concern for #201848 (closed).

See !57062 (comment 562315977) for more context.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because ~"technical debt".
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• 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

Related to #201848 (closed)