docs: fix a sneaky missing comma (CopilotKit#2470)

Author: timcharper

docs/content/docs/langgraph/human-in-the-loop/interrupt-flow.mdx

@@ -153,7 +153,7 @@ We're going to have the agent ask us to name it, so we'll need a state property
 
                 return {
                     ...state,
-                    agentName
+                    agentName,
                     messages: response,
                 };
             }