Add placeholder token in example snippet

doc/user/packages/npm_registry/index.md

@@ -294,11 +294,11 @@ To do this, add lines to your `.npmrc` file, replacing `my-org` with the namespa
 
 ```shell
 @foo:registry=https://gitlab.example.com/api/v4/packages/npm/
-//gitlab.com/api/v4/packages/npm/:_authToken=
+//gitlab.com/api/v4/packages/npm/:_authToken= "<your_token>"
 //gitlab.com/api/v4/projects/<your_project_id>/packages/npm/:_authToken= "<your_token>"
 
 @my-other-org:registry=https://gitlab.example.com/api/v4/packages/npm/
-//gitlab.com/api/v4/packages/npm/:_authToken=
+//gitlab.com/api/v4/packages/npm/:_authToken= "<your_token>"
 //gitlab.com/api/v4/projects/<your_project_id>/packages/npm/:_authToken= "<your_token>"
 ```