Rename class so it works with Rails 7

Author: andyjeffries

app/models/civo/kpi.rb

@@ -1,5 +1,5 @@
 module Civo
-  class KPI < Base
+  class Kpi < Base
     get :stats, "/v#{ENV["CIVO_API_VERSION"] || "2"}/kpi"
   end
 end