* VAULT-21427 change ui references from K/V to KV
* references in docs/
* website json data
* go command errors
* replace Key/Value with Key Value
* add changelog
* update test
* update secret list header badge
* two more test updates
Just a suggestion on how to perhaps improve the language as I found myself re-reading the sentences due to the missing "either ... or ..." having been _told_ that it `can be run in two modes`.