Documentation wrong about including test-pack and http-client

The docs [here ](https://github.com/api-platform/docs/blob/3.1/distribution/testing.md#writing-functional-tests) state;

> If you don't use the distribution, run composer require --dev symfony/test-pack symfony/http-client to install them.

But this is required even when the project is setup through https://github.com/api-platform/api-platform/generate