[#609] Replace zaptest.NewLogger() with zap.L()

Semantic patch:
```
@@
@@
-import "go.uber.org/zap/zaptest"
+import "go.uber.org/zap"

-zaptest.NewLogger(t)
+zap.L()
```

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/services/tree/signature_test.go

@@ -20,7 +20,7 @@ import (
 	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/user"
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/stretchr/testify/require"
-	"go.uber.org/zap/zaptest"
+	"go.uber.org/zap"
 )
 
 type dummyNetmapSource struct {
@@ -97,7 +97,7 @@ func TestMessageSign(t *testing.T) {
 
 	s := &Service{
 		cfg: cfg{
-			log:      &logger.Logger{Logger: zaptest.NewLogger(t)},
+			log:      &logger.Logger{Logger: zap.L()},
 			key:      &privs[0].PrivateKey,
 			nmSource: dummyNetmapSource{},
 			cnrSource: dummyContainerSource{