Update merchandise.html.md - Fixed "list of countries we do not do business in"

The "list of countries we do not do business in" link was broken: https://gitlab.slack.com/archives/C66R8N98F/p1544196019012700

Changed from

https://about.gitlab.com/handbook/sales-process/images_sales_process/#export-control-classification-and-countries-we-do-not-do-business-in-

to this

https://about.gitlab.com/handbook/sales/#export-control-classification-and-countries-we-do-not-do-business-in