fix: update phpstan config and add condition to package setup in src/QUI/ERP/Coupons/Events.php

This commit includes a minor modification in the `phpstan.dist.neon` file where the `excludePaths`
value has been updated. Besides, a conditional check has been added in the `onPackageSetup`
function, under `Events.php` in the `src/QUI/ERP/Coupons` directory, to only proceed if the package
name is 'quiqqer/coupons'. This additional check generally improves the efficiency and correctness
of the package setup process.