[libc++][NFC] Prefer type aliases over structs

Reviewed By: ldionne, #libc

Spies: sstefan1, libcxx-commits, jeroen.dobbelaere

Differential Revision: https://reviews.llvm.org/D134901

NOKEYCHECK=True
GitOrigin-RevId: ed2d3644abee9535eb07333beb1562a651001281
diff --git a/include/array b/include/array
index a145b48..af199ca 100644
--- a/include/array
+++ b/include/array
@@ -266,8 +266,7 @@
     typedef _VSTD::reverse_iterator<iterator>       reverse_iterator;
     typedef _VSTD::reverse_iterator<const_iterator> const_reverse_iterator;
 
-    typedef typename conditional<is_const<_Tp>::value, const char,
-                                char>::type _CharType;
+    typedef __conditional_t<is_const<_Tp>::value, const char, char> _CharType;
 
     struct  _ArrayInStructT { _Tp __data_[1]; };
     _ALIGNAS_TYPE(_ArrayInStructT) _CharType __elems_[sizeof(_ArrayInStructT)];