[libc++][ranges] Fix incorrect integer typedef in elements_view test.

Differential Revision: https://reviews.llvm.org/D142951

(cherry picked from commit 3fe3f9c)

Author: var-const

libcxx/test/std/ranges/range.adaptors/range.elements/sentinel/minus.pass.cpp

@@ -20,6 +20,7 @@
 
 #include <cassert>
 #include <concepts>
+#include <cstddef>
 #include <functional>
 #include <ranges>
 #include <tuple>
@@ -31,7 +32,7 @@ struct Iter {
   std::tuple<int>* it_;
 
   using value_type       = std::tuple<int>;
-  using difference_type  = intptr_t;
+  using difference_type  = std::ptrdiff_t;
   using iterator_concept = std::input_iterator_tag;
 
   constexpr decltype(auto) operator*() const { return *it_; }