Update include/beman/inplace_vector/inplace_vector.hpp

Co-authored-by: Paul T <[email protected]>

Author: wusatosi

include/beman/inplace_vector/inplace_vector.hpp

@@ -495,7 +495,7 @@ struct inplace_vector : private __iv_detail::__storage::_t<__T, __N> {
   using reference = value_type &;
   using const_reference = const value_type &;
   using size_type = size_t;
-  using difference_type = ptrdiff_t;
+  using difference_type = std::ptrdiff_t;
   using iterator = pointer;
   using const_iterator = const_pointer;
   using reverse_iterator = std::reverse_iterator<iterator>;