Update userguide__zh-CN.md

NodeJS sample code:
postgres_uri = vcap_services['postgresql-develop'][0].credentials.uri
postgres_database = vcap_services['postgresql-develop'][0].credentials.database
postgres_host = vcap_services['postgresql-develop'][0].credentials.host1
postgres_port = vcap_services['postgresql-develop'][0].credentials.port1
postgres_user = vcap_services['postgresql-develop'][0].credentials.username
postgres_password = vcap_services['postgresql-develop'][0].credentials.password

documents/Database/PostgreSQL/userguide__zh-CN.md

@@ -144,12 +144,12 @@ postgres_password = vcap_services['postgresql-develop'][0]['credentials']['passw
 
 ```
 vcap_services = process.env.VCAP_SERVICES
-postgres_uri = vcap_services.postgresql-develop[0].credentials.uri
-postgres_database = vcap_services.postgresql-develop[0].credentials.database
-postgres_host = vcap_services.postgresql-develop[0].credentials.host1
-postgres_port = vcap_services.postgresql-develop[0].credentials.port1
-postgres_user = vcap_services.postgresql-developp[0].credentials.username
-postgres_password = vcap_services.postgresql-develop[0].credentials.password
+postgres_uri = vcap_services['postgresql-develop'][0].credentials.uri
+postgres_database = vcap_services['postgresql-develop'][0].credentials.database
+postgres_host = vcap_services['postgresql-develop'][0].credentials.host1
+postgres_port = vcap_services['postgresql-develop'][0].credentials.port1
+postgres_user = vcap_services['postgresql-develop'][0].credentials.username
+postgres_password = vcap_services['postgresql-develop'][0].credentials.password
 ```
 
 ### 步骤四：进阶管理