feat: replace github.com/pkg/errors to errors

Signed-off-by: haoyun <yun.hao@daocloud.io>
Co-authored-by: zounengren <zouyee1989@gmail.com>

cmd/ctr/commands/content/content.go

@@ -17,6 +17,7 @@
 package content
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -31,7 +32,6 @@ import (
 	units "github.com/docker/go-units"
 	digest "github.com/opencontainers/go-digest"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-	"github.com/pkg/errors"
 	"github.com/urfave/cli"
 	exec "golang.org/x/sys/execabs"
 )