Upgrade containerd/imgcrypt and opencontainers/image-spec

- Upgrade github.com/containerd/imgcrypt to prepare for typeurl upgrade
  (see https://github.com/containerd/imgcrypt/pull/72)
- Upgrade github.com/opencontainers/image-spec since imgcrypto needs at
  least 1.0.2.

Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>

vendor/github.com/opencontainers/image-spec/specs-go/v1/descriptor.go

@@ -35,6 +35,11 @@ type Descriptor struct {
 	// Annotations contains arbitrary metadata relating to the targeted content.
 	Annotations map[string]string `json:"annotations,omitempty"`
 
+	// Data is an embedding of the targeted content. This is encoded as a base64
+	// string when marshalled to JSON (automatically, by encoding/json). If
+	// present, Data can be used directly to avoid fetching the targeted content.
+	Data []byte `json:"data,omitempty"`
+
 	// Platform describes the platform which the image in the manifest runs on.
 	//
 	// This should only be used when referring to a manifest.