Update UploadEnhancedConversionsForLeads.java

Add comment specifying that session attributes is only available by allowlist.

Author: BenRKarl

google-ads-examples/src/main/java/com/google/ads/googleads/examples/remarketing/UploadEnhancedConversionsForLeads.java

@@ -308,7 +308,8 @@ private void runExample(
 
     // [START add_session_attributes]
     // Sets one of the sessionAttributesEncoded or sessionAttributesKeyValuePairs if either is
-    // provided.
+    // provided. The session attribute fields are only available to allowlisted users.
+    // To include these fields in conversion imports, upgrade to the Data Manager API.
     if (rawRecord.containsKey("sessionAttributesEncoded")) {
       clickConversionBuilder.setSessionAttributesEncoded(
           ByteString.copyFromUtf8(rawRecord.get("sessionAttributesEncoded")));