DEVX-813: fixing NotNull annotation

Author: ShipilA

commercetools/commercetools-importapi-utils/src/main/java/com/commercetools/sdk/ProductUtil.java

@@ -26,7 +26,7 @@
 import com.commercetools.importapi.models.products.ProductImport;
 import com.commercetools.importapi.models.productvariants.Attribute;
 
-import org.jetbrains.annotations.NotNull;
+import jakarta.validation.constraints.NotNull;
 
 public class ProductUtil {
     private final KeyResolverService keyResolverService;