docs: update iam postgresql sample code host (#514)

Author: crystall-bitquill

examples/aws_driver_example/aws_iam_authentication_postgresql_example.ts

@@ -17,7 +17,7 @@
 import { readFileSync } from "fs";
 import { AwsPGClient } from "../../pg/lib";
 
-const postgresHost = "postgresql://db-identifier.XYZ.us-east-2.rds.amazonaws.com";
+const postgresHost = "db-identifier.XYZ.us-east-2.rds.amazonaws.com";
 const username = "john_smith";
 const database = "employees";
 const port = 5432;