Remove Git annex pages from left navigation
Related to gitlab#328651 (closed) where the pages will be removed.
- doc_title: Git annex
doc_url: 'ee/administration/git_annex.html'
- doc_title: Git LFS to Git annex migration
doc_url: 'ee/topics/git/lfs/migrate_from_git_annex_to_git_lfs.html'