cleanup - thanks @Kerndog73

src/entt/meta/meta.hpp

@@ -645,8 +645,6 @@ public:
      * @param rhs A valid meta any object.
      */
     friend void swap(meta_any &lhs, meta_any &rhs) ENTT_NOEXCEPT {
-        using std::swap;
-
         if(lhs && rhs) {
             storage_type buffer;
             void *instance = lhs.steal_fn(buffer, lhs.storage, lhs.destroy_fn, lhs.instance);

src/entt/signal/sigh.hpp

@@ -138,16 +138,6 @@ public:
         }
     }
 
-    /**
-     * @brief Swaps listeners between the two signals.
-     * @param lhs A valid signal object.
-     * @param rhs A valid signal object.
-     */
-    friend void swap(sigh &lhs, sigh &rhs) {
-        using std::swap;
-        swap(lhs.calls, rhs.calls);
-    }
-
 private:
     std::vector<delegate<Ret(Args...)>> calls;
 };