DA - gb csv modal

fixes CNVS-15487

test plan:
 - open the gb csv upload modal
 - click the link to learn more
 > it should open a new tab and take you to the guide pages

Change-Id: Ief4cffbdac0a59de8896ae8c17c2cde28d0d6311
Reviewed-on: https://gerrit.instructure.com/41175
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Anna Koalenz <akoalenz@instructure.com>
Reviewed-by: Mike Nomitch <mnomitch@instructure.com>
Product-Review: Cameron Sutter <csutter@instructure.com>