srgb - persist show concluded enrollments

fixes CNVS-12034

test plan
- in srgb, enable show concluded enrollments
- refresh srgb, verify that it persists
- check gb2, verify that the setting persists
- disable the setting in srgb
- verify in srgb and gb2 that it is disabled
- in gb2, enable and disable
- verify that srgb setting matches that set in gb2

Change-Id: Ic62384c5757759c440edf4c5b392a776d4dbb30f
Reviewed-on: https://gerrit.instructure.com/32883
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Mike Nomitch <mnomitch@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Liz Abinante <labinante@instructure.com>