Revert "Fix precedence of default tasks over custom ones in registry"

This reverts commit 8125ea2.

src/lighteval/tasks/registry.py

@@ -152,7 +152,7 @@ def task_registry(self):
             )
 
         # Defaults tasks should overwrite custom tasks
-        return {**custom_tasks_registry, **default_tasks_registry}
+        return {**default_tasks_registry, **custom_tasks_registry}
 
     @property
     @lru_cache