Update UPGRADE-1.12.md
Update UPGRADE-1.12.md

Co-authored-by: Jan Góralski <510bb9a103421591ea4b951e5bd7a3d35b829b5f@gmail.com>
Sylius/Sylius,diimpp/Sylius,diimpp/Sylius,Sylius/Sylius,diimpp/Sylius,Sylius/Sylius