Correctly display EE downloads in /installation
https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/6107 introduced some changes to the /installation
page,
but it missed to display EE packages by default. This MR fixes that and adds some missing links.
Relevant issue https://gitlab.com/gitlab-com/www-gitlab-com/issues/1336
Closes https://gitlab.com/gitlab-com/www-gitlab-com/issues/1448
Edited by Achilleas Pipinellis