fix(retail): add region tag for node.js - Update set inventory

retail/interactive-tutorials/product/set-inventory.js

@@ -11,7 +11,8 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-
+// [START retail_set_inventory]
+//
 'use strict';
 
 async function main(generatedProductId) {
@@ -99,3 +100,5 @@ process.on('unhandledRejection', err => {
 });
 
 main(...process.argv.slice(2));
+//
+// [END retail_set_inventory]