README: drop Symfony 2.8 note since Symfony 4 is comming soon

Author: Tomáš Votruba

README.md

@@ -67,17 +67,3 @@ terminal.
 > Symfony Demo application, configure it to point at the `web/` directory of the project.
 > For more details, see:
 > https://symfony.com/doc/current/cookbook/configuration/web_server_configuration.html
-
-Troubleshooting
----------------
-
-The current Symfony Demo application uses Symfony 3.x version. If you want to
-use the legacy Symfony 2.8 version, clone the Git repository and checkout the
-`v0.8.4` tag, which is the last one compatible with Symfony 2.8:
-
-```bash
-$ git clone https://github.com/symfony/symfony-demo symfony_demo
-$ cd symfony_demo/
-$ git checkout tags/v0.8.4 -b v0.8.4
-$ composer install
-```