Remove brief_links macro as no longer used in this app
Remove brief_links macro as no longer used in this app

We no longer use the brief_links macro since the briefs app
got split out of the buyer app. This macro still exists in the
briefs app but is no longer needed in this one.

alphagov/digitalmarketplace-buyer-frontend,alphagov/digitalmarketplace-buyer-frontend,alphagov/digitalmarketplace-buyer-frontend,alphagov/digitalmarketplace-buyer-frontend