cli/config/credentials: remove uses of pkg/errors in tests

While there may be reasons to keep pkg/errors in production code,
we don't need them for these tests.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

cli/config/credentials/native_store_test.go

@@ -2,6 +2,7 @@ package credentials
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"strings"
@@ -10,7 +11,6 @@ import (
 	"github.com/docker/cli/cli/config/types"
 	"github.com/docker/docker-credential-helpers/client"
 	"github.com/docker/docker-credential-helpers/credentials"
-	"github.com/pkg/errors"
 	"gotest.tools/v3/assert"
 	is "gotest.tools/v3/assert/cmp"
 )
@@ -22,7 +22,7 @@ const (
 	missingCredsAddress  = "https://missing.docker.io/v1"
 )
 
-var errCommandExited = errors.Errorf("exited 1")
+var errCommandExited = errors.New("exited 1")
 
 // mockCommand simulates interactions between the docker client and a remote
 // credentials helper.