Update vendor files to fix build failure

Signed-off-by: Chifeng Cai <frcai@microsoft.com>

vendor/golang.org/x/net/html/doc.go

@@ -78,16 +78,11 @@ example, to process each anchor node in depth-first order:
 	if err != nil {
 		// ...
 	}
-	var f func(*html.Node)
-	f = func(n *html.Node) {
+	for n := range doc.Descendants() {
 		if n.Type == html.ElementNode && n.Data == "a" {
 			// Do something with n...
 		}
-		for c := n.FirstChild; c != nil; c = c.NextSibling {
-			f(c)
-		}
 	}
-	f(doc)
 
 The relevant specifications include:
 https://html.spec.whatwg.org/multipage/syntax.html and