Update ChatGPT default model

The default ChatGPT model is now set to the latest release, `gpt-4o`.

Change-Id: I1e8ab469c3c72595570863491fda1267d7cec200
Signed-off-by: Patrizio <patrizio.gelosi@amarulasolutions.com>
diff --git a/src/main/java/com/googlesource/gerrit/plugins/chatgpt/config/Configuration.java b/src/main/java/com/googlesource/gerrit/plugins/chatgpt/config/Configuration.java
index dddced3..0a26d62 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/chatgpt/config/Configuration.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/chatgpt/config/Configuration.java
@@ -24,7 +24,7 @@
 
     // Default Config values
     public static final String OPENAI_DOMAIN = "https://api.openai.com";
-    public static final String DEFAULT_GPT_MODEL = "gpt-3.5-turbo";
+    public static final String DEFAULT_GPT_MODEL = "gpt-4o";
     public static final double DEFAULT_GPT_REVIEW_TEMPERATURE = 0.2;
     public static final double DEFAULT_GPT_COMMENT_TEMPERATURE = 1.0;