fixup! improve metadata handling concepts

Author: aalkin

Framework/Core/include/Framework/ASoA.h

@@ -221,7 +221,7 @@ template <typename T>
 concept has_metadata = is_metadata_trait<T> && not_void<typename T::metadata>;
 
 template <typename T>
-concept has_sources = is_metadata_trait<T> && not_void<typename T::sources>;
+concept has_sources = is_metadata<T> && not_void<typename T::sources>;
 
 template <typename T>
 concept is_spawnable_column = std::is_same_v<typename T::spawnable_t, std::true_type>;