Add Reduce repo size entry to navigation
Adds https://docs.gitlab.com/ee/user/project/repository/reducing_the_repo_size_using_git.html to the global navigation.
Relates to: gitlab!33576 (merged).
Adds https://docs.gitlab.com/ee/user/project/repository/reducing_the_repo_size_using_git.html to the global navigation.
Relates to: gitlab!33576 (merged).