Change the comment on the closing #endif to match the condition on the corresponding #ifdef. Thanks to K-ballo for the catch. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@220647 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/experimental/optional b/include/experimental/optional
index 41d86b4..2f0df35 100644
--- a/include/experimental/optional
+++ b/include/experimental/optional
@@ -692,4 +692,4 @@
 
 #endif  // _LIBCPP_STD_VER > 11
 
-#endif  // _LIBCPP_ARRAY
+#endif  // _LIBCPP_OPTIONAL