Revert "SE-3629 Store MKTG_URL_LINK_MAP in EDXAPP_MKTG_URL_LINK_MAP"

Created by: nizarmah

Reverts open-craft/opencraft#675

The reason we're reverting this change can be found in this mattermost discussion

This will result in breaking the integration tests again, so we'll need to include them again in the next change cc @s0b0lev