i18n: remove explicit formencode language setting

Does not seem to be needed anymore, formencode validation is still
translated in the current language without it.

kallithea/config/app_cfg.py

@@ -174,8 +174,6 b' def setup_configuration(app):'
         repo2db_mapper(ScmModel().repo_scan(repos_path),
                        remove_obsolete=False, install_git_hooks=False)
 
-    formencode.api.set_stdtranslation(languages=[config.get('lang')])
-
 hooks.register('configure_new_app', setup_configuration)