AdminFilter.php is in \admin\autoupgrade\latest\src\PrestaShopBundle\Entity\
You can add the lines in this file as mentioned before
Clean your cache + delete /dev and /prod folder in /var/cache
reload your admin page at BO > Catalog > products
If it does not work already, now go to \src\PrestaShopBundle\Entity\ to find the other AdminFilter.php and add also the lines as mentioned before
Re-clean your cache.
If the module continue to not working correctly with prestashop 1.7.4, I make a try with prestashop 1.7.4...
