[libcxx-commits] [libcxx] [libc++] Update container adaptors' tests (PR #224810)

[A. Jiang via libcxx-commits]

================
@@ -74,7 +74,8 @@ class flat_multiset {
 
   friend __flat_set_utils;
 
-  static_assert(is_same_v<_Key, typename _KeyContainer::value_type>);
+  static_assert(is_same_v<_Key, typename _KeyContainer::value_type>,
+                "The stored elements key type must match the underlying container's key value_type.");
----------------
frederick-vs-ja wrote:

```suggestion
  static_assert(is_same_v<_Key, typename _KeyContainer::value_type>,
                "The stored elements key type must match the underlying key container's value_type.");
```

https://github.com/llvm/llvm-project/pull/224810