Update GraphQL DuoChat docs

This MR updates the DuoChat GraphQL Docs.

It removes some outdated information and removes GraphQL Query variables that are no longer needed.

doc/development/ai_features/duo_chat.md

@@ -375,7 +375,7 @@ The GraphQL Subscription for Chat behaves slightly different because it's user-c
 We therefore need to broadcast messages to multiple clients to keep them in sync. The `aiAction` mutation with the `chat` action behaves the following:
 
 1. All complete Chat messages (including messages from the user) are broadcasted with the `userId`, `aiAction: "chat"` as identifier.
-1. Chunks from streamed Chat messages and slash commands are broadcasted with the `clientSubscriptionId` from the mutation as identifier.
+1. Chunks from streamed Chat messages are broadcasted with the `clientSubscriptionId` from the mutation as identifier.
 
 Examples of GraphQL Subscriptions in a Vue component:
 
@@ -419,7+419,7 @@
             aiAction: 'CHAT',
             clientSubscriptionId // randomly generated identifier for every message
             htmlResponse: false, // important to bypass HTML processing on every chunk
           };
         },
         result({ data }) {
           // handle data.aiCompletionResponse