Symfony v3.x: translator.class

[n-sviridenko]

Hello!

I found mention about the translator.class in the symfony 3.1 documentation http://symfony.com/doc/current/bundles/override.html#services-configuration. But this possibility was dropped in the v3. This part of docs is outdated.

[javiereguiluz]

@n-sviridenko thanks for reporting this error. We're fixing it in #6927.