Update synopsis for list/forward_list/deque to match the allocator style of existing comment. No code change

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@190320 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/list b/include/list
index f37cffd..800a1a3 100644
--- a/include/list
+++ b/include/list
@@ -40,7 +40,7 @@
         noexcept(is_nothrow_default_constructible<allocator_type>::value);
     explicit list(const allocator_type& a);
     explicit list(size_type n);
-    explicit list(size_type n, const Allocator& a); // C++14
+    explicit list(size_type n, const allocator_type& a); // C++14
     list(size_type n, const value_type& value);
     list(size_type n, const value_type& value, const allocator_type& a);
     template <class Iter>