Add trailing comma

Author: rattrayalex

openapi.yaml

@@ -153,7 +153,7 @@ paths:
                     model: 'gpt-3.5-turbo',
                     messages: [
                       {"role": "system", "content": "You are a helpful assistant."},
-                      {"role": "user", "content": "Hello!"}
+                      {"role": "user", "content": "Hello!"},
                     ],
                     stream: true,
                   });