Fix broken master: Add detected_repository_languages to schema.rb

What does this MR do?

Adds a missing property projects.detected_repository_languages to schema.rb.

This property is present in the ce schema, but is absent in the ee schema.

It must have happened when the ce schema.rb was merged into ee schema.rb, and there was a conflict between the new projects.detected_repository_languages property in ce master and projects.merge_requests_require_code_owner_approval which had just been added to ee master. This was auto-resolved to prefer the version in ee.

Fixes master:broken

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/10858

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer