Add temp to ignored folders for code sniffer

The folder is created by PHPStan and contains PHPStan cache.
It doesn't cause any errors but including it makes the check much longer.

[MAILPOET-3889]

RoboFile.php

@@ -389,6 +389,7 @@ class RoboFile extends \Robo\Tasks {
       'tasks/phpstan/vendor',
       'tasks/makepot',
       'tools/vendor',
+      'temp',
       'tests/_data',
       'tests/_output',
       'tests/_support/_generated',