Update the 9.0.x branch to Symfony 4.4-rc1 or 5.0-rc1

The release candidate (symfony 4 and 5) is released as of 17-11-2019. (rc-1).

https://symfony.com/blog/symfony-4-4-0-rc1-released

https://symfony.com/blog/symfony-5-0-0-rc1-released.