GroupByQueryConfig: Skip unnecessary toString. (#17396)

Calling toString on newConfig is unnecessary, because it will be done
automatically by the logger. This saves some effort under log levels
higher than DEBUG.

processing/src/main/java/org/apache/druid/query/groupby/GroupByQueryConfig.java

@@ -370,7 +370,7 @@ public GroupByQueryConfig withOverrides(final GroupByQuery query)
         isMultiValueUnnestingEnabled()
     );
 
-    logger.debug("Override config for GroupBy query %s - %s", query.getId(), newConfig.toString());
+    logger.debug("Override config for GroupBy query %s - %s", query.getId(), newConfig);
     return newConfig;
   }