Merge branch 'doc/fix_update_doc_links' into 'master'

Fix links in Update guide 5.1 to 6.0

Links have missing slashes and additionally point to `master` branch.
This MR prevents a 404 error (missing slash) and points to the correct branch (6-0-stable) for comparison of the config files.

/cc @sytse

doc/update/5.1-to-6.0.md

@@ -95,8 +95,8 @@ sudo -u git -H bundle exec rake assets:precompile RAILS_ENV=production
 
 Note: We switched from Puma in GitLab 5.x to unicorn in GitLab 6.0.
 
-- Make `/home/git/gitlab/config/gitlab.yml` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/masterconfig/gitlab.yml.example but with your settings.
-- Make `/home/git/gitlab/config/unicorn.rb` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/masterconfig/unicorn.rb.example but with your settings.
+- Make `/home/git/gitlab/config/gitlab.yml` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/6-0-stable/config/gitlab.yml.example but with your settings.
+- Make `/home/git/gitlab/config/unicorn.rb` the same as https://gitlab.com/gitlab-org/gitlab-ce/blob/6-0-stable/config/unicorn.rb.example but with your settings.
 
 ## 7. Update Init script