Revert "i18n: Ensure UTF-8 locale is set"

bootstrap.php

@@ -290,10 +290,6 @@ class Bootstrap {
         }
         if (extension_loaded('iconv'))
             iconv_set_encoding('internal_encoding', 'UTF-8');
-
-        // Set the default locale to UTF-8. It will be changed by
-        // ::setLocaleForUser() later for web requests. See #2910
-        Translation::setLocale(LC_ALL, 'en_US.UTF-8');
     }
 
     function croak($message) {