graph: discard the no longer necessary operator!=

src/entt/graph/adjacency_matrix.hpp

@@ -79,11 +79,6 @@ template<typename Container>
     return lhs.pos == rhs.pos;
 }
 
-template<typename Container>
-[[nodiscard]] constexpr bool operator!=(const edge_iterator<Container> &lhs, const edge_iterator<Container> &rhs) noexcept {
-    return !(lhs == rhs);
-}
-
 } // namespace internal
 /*! @endcond */