fix: use value dereference for v2error.Error with %w

Signed-off-by: Sharath P J <pjsharath28@gmail.com>

Author: pjsharath28

server/etcdserver/api/v2store/store.go

@@ -535,7 +535,7 @@ func (s *store) Update(nodePath string, newValue string, expireOpts TTLOptionSet
 	eNode := e.Node
 
 	if err := n.Write(newValue, nextIndex); err != nil {
-		return nil, fmt.Errorf("nodePath %v : %w", nodePath, err)
+		return nil, fmt.Errorf("nodePath %v : %w", nodePath, *err)
 	}
 
 	if n.IsDir() {