Backward compatibility

app/src/main/java/eu/faircode/email/OpenAI.java

@@ -149,8 +149,10 @@ public class OpenAI {
 
         JSONObject jquestion = new JSONObject();
         jquestion.put("model", model);
-        if (max_tokens > 0)
+        if (max_tokens > 0) {
+            jquestion.put("max_tokens", max_tokens);
             jquestion.put("max_completion_tokens", max_tokens);
+        }
         jquestion.put("messages", jmessages);
         if (temperature != null)
             jquestion.put("temperature", temperature);