Update vendor

vendor/golang.org/x/net/http2/not_go115.go

@@ -0,0 +1,31 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.15
+// +build !go1.15
+
+package http2
+
+import (
+	"context"
+	"crypto/tls"
+)
+
+// dialTLSWithContext opens a TLS connection.
+func (t *Transport) dialTLSWithContext(ctx context.Context, network, addr string, cfg *tls.Config) (*tls.Conn, error) {
+	cn, err := tls.Dial(network, addr, cfg)
+	if err != nil {
+		return nil, err
+	}
+	if err := cn.Handshake(); err != nil {
+		return nil, err
+	}
+	if cfg.InsecureSkipVerify {
+		return cn, nil
+	}
+	if err := cn.VerifyHostname(cfg.ServerName); err != nil {
+		return nil, err
+	}
+	return cn, nil
+}