doc: drop unused comments

src/entt/poly/poly.hpp

@@ -190,7 +190,6 @@ decltype(auto) poly_call(Poly &&self, Args &&...args) {
  */
 template<typename Concept, std::size_t Len, std::size_t Align>
 class basic_poly: private Concept::template type<poly_base<basic_poly<Concept, Len, Align>>> {
-    /*! @brief A poly base is allowed to snoop into a poly object. */
     friend struct poly_base<basic_poly>;
 
 public:

src/entt/resource/resource.hpp

@@ -20,7 +20,6 @@ namespace entt {
  */
 template<typename Type>
 class resource {
-    /*! @brief Resource handles are friends with each other. */
     template<typename>
     friend class resource;
 

src/entt/signal/sigh.hpp

@@ -52,7 +52,6 @@ class sigh;
  */
 template<typename Ret, typename... Args, typename Allocator>
 class sigh<Ret(Args...), Allocator> {
-    /*! @brief A sink is allowed to modify a signal. */
     friend class sink<sigh<Ret(Args...), Allocator>>;
 
     using alloc_traits = std::allocator_traits<Allocator>;
@@ -225,7 +224,6 @@ private:
  * the sink that generated it.
  */
 class connection {
-    /*! @brief A sink is allowed to create connection objects. */
     template<typename>
     friend class sink;