build: remove entt library

include/entt/graph/fwd.hpp

@@ -1,28 +0,0 @@
-#ifndef ENTT_GRAPH_FWD_HPP
-#define ENTT_GRAPH_FWD_HPP
-
-#include "../core/fwd.hpp"
-#include "../stl/concepts.hpp"
-#include "../stl/cstddef.hpp"
-#include "../stl/memory.hpp"
-
-namespace entt {
-
-/*! @brief Undirected graph category tag. */
-struct directed_tag {};
-
-/*! @brief Directed graph category tag. */
-struct undirected_tag: directed_tag {};
-
-template<stl::derived_from<directed_tag>, typename = stl::allocator<stl::size_t>>
-class adjacency_matrix;
-
-template<typename = stl::allocator<id_type>>
-class basic_flow;
-
-/*! @brief Alias declaration for the most common use case. */
-using flow = basic_flow<>;
-
-} // namespace entt
-
-#endif