De-dupe refresh service EE spec

What does this MR do?

Part of !27556 (merged)

This moves the specs from /ee/spec/services/merge_requests/refresh_service_spec.rb to /ee/spec/services/ee/merge_requests/refresh_service_spec.rb.

Note: Since the specs of the file I've moved were a bit different (e.g. using instance variables instead of let), I've split the commits into multiple ones so it was easier to move and easier to read for the reviewer.

Screenshots

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

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

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• 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
• Security reports checked/validated by a reviewer from the AppSec team