horse: finish rename of trainee -> uma in koka

horsegen/skill.kk.template

@@ -193,11 +193,11 @@ pub fun activations(s: skill-id): list<activation>
 // Get the owner of a unique skill.
 // If the skill is not unique, or if there is no skill with the given ID,
 // the result is Nothing.
-pub fun unique-owner(s: skill-id): maybe<trainee-id>
+pub fun unique-owner(s: skill-id): maybe<uma-id>
   match s.game-id
     {{- range $s := $.Skills }}
     {{- if $s.UniqueOwnerID }}
-    {{ $s.ID }} -> Just(Trainee-id({{ $s.UniqueOwnerID }}))
+    {{ $s.ID }} -> Just(Uma-id({{ $s.UniqueOwnerID }}))
     {{- end }}
     {{- end }}
     _ -> Nothing