Reorganize the reference architecture items in the navbar
In gitlab!31485 (merged), we split the reference architectures into their own individual pages.
There's also an ongoing effort to get the pages under the high_availability/
dir to the higher administration/
level gitlab#214353 (closed). Until we do that, let's get the new pages under the ref arches, and move the ones under HA up one level.
Edited by Achilleas Pipinellis