cli/command/image: remove TestAddTargetToAllSignableRolesError

This test was only testing trust.GetSignableRoles to return an error
if it's offline, which was duplicating the [TestGetSignableRolesError]
test in the cli/trust package.

[TestGetSignableRolesError]: https://github.com/docker/cli/blob/fe0a8d27912dc6fddc60cedcd35bbef27b776355/cli/trust/trust_test.go#L49-L55

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

cli/command/image/trust_test.go

@@ -5,10 +5,6 @@ import (
 
 	"github.com/docker/cli/cli/trust"
 	registrytypes "github.com/docker/docker/api/types/registry"
-	"github.com/theupdateframework/notary/client"
-	"github.com/theupdateframework/notary/passphrase"
-	"github.com/theupdateframework/notary/trustpinning"
-	"gotest.tools/v3/assert"
 	"gotest.tools/v3/env"
 )
 
@@ -47,11 +43,3 @@ func TestNonOfficialTrustServer(t *testing.T) {
 		t.Fatalf("Expected server to be %s, got %s", expectedStr, output)
 	}
 }
-
-func TestAddTargetToAllSignableRolesError(t *testing.T) {
-	notaryRepo, err := client.NewFileCachedRepository(t.TempDir(), "gun", "https://localhost", nil, passphrase.ConstantRetriever("password"), trustpinning.TrustPinConfig{})
-	assert.NilError(t, err)
-	target := client.Target{}
-	err = AddTargetToAllSignableRoles(notaryRepo, &target)
-	assert.Error(t, err, "client is offline")
-}