[ADT] Use std::is_copy_constructible_v (NFC)

Author: kazutakahirata

llvm/include/llvm/ADT/MapVector.h

@@ -109,7 +109,7 @@ class MapVector {
 
   // Returns a copy of the value.  Only allowed if ValueT is copyable.
   ValueT lookup(const KeyT &Key) const {
-    static_assert(std::is_copy_constructible<ValueT>::value,
+    static_assert(std::is_copy_constructible_v<ValueT>,
                   "Cannot call lookup() if ValueT is not copyable.");
     typename MapType::const_iterator Pos = Map.find(Key);
     return Pos == Map.end()? ValueT() : Vector[Pos->second].second;