Remove use of legacy ACS import endpoint

The original idea was to merge the switch to the new ACS export/import endpoints before the migration to 3.4 and then the legacy import endpoint would be used for the migration while after the migration everything is on 3.4.

I think we may actually have merged the change only after the migration so it made no real sense and even if we did we are on 3.4 now so we can nuke it.