DA - unhide feature flag

fixes CNVS-17452

test plan:
  as account admin that is not a non-siteadmin, 
  make sure you can enable DA for your root account

Change-Id: I6c904c50f89d78a757f709cb2bd16a6d7c2218ff
Reviewed-on: https://gerrit.instructure.com/45656
Reviewed-by: Simon Williams <simon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Sean Lewis <slewis@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>