[cs] Remove psr0 check

Project is PSR-4 compliant and php-cs-fixer psr0 is bugged (sometimes change to lowercase subnamaspace PHP-CS-Fixer/PHP-CS-Fixer#1161)

.php_cs

@@ -31,7 +31,6 @@ $config->fixers(
         'method_argument_space',
         'object_operator',
         'php_closing_tag',
-        'psr0',
         'remove_lines_between_uses',
         'short_tag',
         'standardize_not_equal',