Edit History

Hello,
I'm developing an online shop with prestashop 1.7.5.1, and I want to remove "Powered by Prestashop" from New Order Email,
I removed it from International/Translation, i removed it manually from translation folder, also from the module ps_emailalert... and app/translations/ folder and many othoer locations.
then I cleaned the cache. 
And at my surprise, it's always present in the emails.
Please, how to remove that ?

Thanks