test: replace unnecessary `CreateResourceFromStringWithNamespace` with `CreateResourceFromString`

Some code uses `CreateResourceFromStringWithNamespace`, but it is unnecessary, and it can be considered to be replaced with `CreateResourceFromString`.

```
gatewayProxyName := s.Namespace()
err = s.CreateResourceFromStringWithNamespace(fmt.Sprintf(defaultGatewayProxy, gatewayProxyName, s.Deployer.GetAdminEndpoint(), s.AdminKey()), s.Namespace())
```