Update github.com/containerd/containerd to v1.5.7

... to include a fix for
https://github.com/advisories/GHSA-c2h3-6mxw-7mvq .

(Note that Skopeo doesn't depend on the vulnerable code,
so this is primarily to avoid dependency checker warnings.)

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/google.golang.org/grpc/internal/credentials/spiffe.go

@@ -1,5 +1,3 @@
-// +build !appengine
-
 /*
  *
  * Copyright 2020 gRPC authors.

vendor/google.golang.org/grpc/internal/credentials/spiffe_appengine.go

@@ -1,31 +0,0 @@
-// +build appengine
-
-/*
- *
- * Copyright 2020 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-package credentials
-
-import (
-	"crypto/tls"
-	"net/url"
-)
-
-// SPIFFEIDFromState is a no-op for appengine builds.
-func SPIFFEIDFromState(state tls.ConnectionState) *url.URL {
-	return nil
-}

vendor/google.golang.org/grpc/internal/credentials/syscallconn.go

@@ -1,5 +1,3 @@
-// +build !appengine
-
 /*
  *
  * Copyright 2018 gRPC authors.

vendor/google.golang.org/grpc/internal/credentials/syscallconn_appengine.go

@@ -1,30 +0,0 @@
-// +build appengine
-
-/*
- *
- * Copyright 2018 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-package credentials
-
-import (
-	"net"
-)
-
-// WrapSyscallConn returns newConn on appengine.
-func WrapSyscallConn(rawConn, newConn net.Conn) net.Conn {
-	return newConn
-}

vendor/google.golang.org/grpc/internal/credentials/util.go

@@ -18,7 +18,9 @@
 
 package credentials
 
-import "crypto/tls"
+import (
+	"crypto/tls"
+)
 
 const alpnProtoStrH2 = "h2"