Remove duplicated metadata

When approving a MR that touched this page, I noticed after the fact
that the metadata was doubled. This MR removes the duplicate data.

doc/user/project/repository/repository_mirroring.md

@@ -3,9 +3,6 @@ stage: Create
 group: Source Code
 info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 disqus_identifier: 'https://docs.gitlab.com/ee/workflow/repository_mirroring.html'
-stage: Create
-group: Source Code
-info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 ---
 
 # Repository mirroring