update vendor

Signed-off-by: Roland.Ma <rolandma@yunify.com>

vendor/golang.org/x/net/http2/write.go

@@ -341,7 +341,12 @@ func encodeHeaders(enc *hpack.Encoder, h http.Header, keys []string) {
 	}
 	for _, k := range keys {
 		vv := h[k]
-		k = lowerHeader(k)
+		k, ascii := lowerHeader(k)
+		if !ascii {
+			// Skip writing invalid headers. Per RFC 7540, Section 8.1.2, header
+			// field names have to be ASCII characters (just as in HTTP/1.x).
+			continue
+		}
 		if !validWireHeaderFieldName(k) {
 			// Skip it as backup paranoia. Per
 			// golang.org/issue/14048, these should