[FIX] remove purchase_ok from demo data as it is not a field of product.product
[FIX] remove purchase_ok from demo data as it is not a field of product.product

This should make runbot green.

raycarnes/account-closing,yvaucher/account-closing,dvitme/account-closing,Endika/account-closing,open-synergy/account-closing,xpansa/account-closing,acsone/account-closing