meta: removed as_ref tag

src/entt/meta/policy.hpp

@@ -9,10 +9,6 @@ namespace entt {
 struct as_ref_t {};
 
 
-/*! @brief Disambiguation tag. */
-inline constexpr as_ref_t as_ref;
-
-
 /*! @brief Empty class type used to request the _as-is_ policy. */
 struct as_is_t {};