Drop Turkish, Russian and Romanian translations from official list

[wouterj]

Non maintained languages are removed from the official list of repositories as obsolete documentation is dangerous.
-- http://symfony.com/doc/current/contributing/documentation/translations.html#maintenance

There are 3 translations which are last updated one year ago (or even more):

• https://github.com/sebio/symfony-docs-ro
• https://github.com/avalanche123/symfony-docs-ru
• https://github.com/symfony-tr/symfony-docs-tr

IMO, that means that they should be removed from the list?

/cc @symfony/team-symfony-docs
/cc @bogacaslan @import @sedatkocadogan
/cc @avalanche123 @frost-nzcr4 @dbykadorov @Skorney
/cc @sebio

[fabpot]

Looks fine to me.