Update vendor (#1498)

vendor/golang.org/x/crypto/ed25519/ed25519.go

@@ -5,6 +5,7 @@
 // In Go 1.13, the ed25519 package was promoted to the standard library as
 // crypto/ed25519, and this package became a wrapper for the standard library one.
 //
+//go:build !go1.13
 // +build !go1.13
 
 // Package ed25519 implements the Ed25519 signature algorithm. See

vendor/golang.org/x/crypto/ed25519/ed25519_go113.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build go1.13
 // +build go1.13
 
 // Package ed25519 implements the Ed25519 signature algorithm. See