registry: reduce impact of entity_like, and prepare to fix it

src/entt/entity/fwd.hpp

@@ -59,7 +59,7 @@ class basic_sigh_mixin;
 template<typename, typename>
 class basic_reactive_mixin;
 
-template<entity_like Entity = entity, typename = std::allocator<Entity>>
+template<typename Entity = entity, typename = std::allocator<Entity>>
 class basic_registry;
 
 template<typename, typename>

src/entt/entity/registry.hpp

@@ -210,7 +210,7 @@ private:
  * @tparam Entity A valid entity type.
  * @tparam Allocator Type of allocator used to manage memory and elements.
  */
-template<entity_like Entity, typename Allocator>
+template<typename Entity, typename Allocator>
 class basic_registry {
     using base_type = basic_sparse_set<Entity, Allocator>;
     using alloc_traits = std::allocator_traits<Allocator>;