refactor(docs/uml): make GitlabTicketResponse inner class name unique

docs/developers-guide/uml.md

@@ -346,7 +346,7 @@ class GitlabTicketResponse {
     # constructor()
 }
 
-class Assignee {
+class GitlabTicketResponse.Assignee {
     + id: int
     + name: String
     + username: String
@@ -392,7 +392,7 @@ class GitlabTicketSystemBuilder {
 
 ' package connections
 GitlabFilter o-- GitlabTicketSystem: "parent"
-GitlabTicketResponse o- Assignee: "inner class"
+GitlabTicketResponse o- GitlabTicketResponse.Assignee: "inner class"
 GitlabTicketSystemBuilder --> GitlabTicketSystem: "build()"
 GitlabTicketSystem --> GitlabTicketBuilder: "createTicket()"
 GitlabTicketBuilder --> GitlabTicket: "create()"