[libc++][NFC] Remove _VSTD:: when not needed.

Reviewed By: #libc, Quuxplusone

Differential Revision: https://reviews.llvm.org/D102133

NOKEYCHECK=True
GitOrigin-RevId: cfef7c918b8297ffb1d882d6b31fe68f876607db
diff --git a/include/concepts b/include/concepts
index 39c1f63..7195b3b 100644
--- a/include/concepts
+++ b/include/concepts
@@ -217,12 +217,12 @@
 // [concept.destructible]
 
 template<class _Tp>
-concept destructible = _VSTD::is_nothrow_destructible_v<_Tp>;
+concept destructible = is_nothrow_destructible_v<_Tp>;
 
 // [concept.constructible]
 template<class _Tp, class... _Args>
 concept constructible_from =
-    destructible<_Tp> && _VSTD::is_constructible_v<_Tp, _Args...>;
+    destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
 
 // [concept.default.init]