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/forward_list b/include/forward_list
index 2fbcdbe..398226b 100644
--- a/include/forward_list
+++ b/include/forward_list
@@ -38,7 +38,7 @@
         noexcept(is_nothrow_default_constructible<allocator_type>::value);
     explicit forward_list(const allocator_type& a);
     explicit forward_list(size_type n);
-    explicit forward_list(size_type n, const Allocator& a); // C++14
+    explicit forward_list(size_type n, const allocator_type& a); // C++14
     forward_list(size_type n, const value_type& v);
     forward_list(size_type n, const value_type& v, const allocator_type& a);
     template <class InputIterator>