re-hide features when site admin turns them off

previously, this worked only in site admin context. this commit
makes it work in any context.

test plan:
 1. as site admin user A, go to the Features tab of the
    account settings for the Site Admin account and find a
    feature with the 'hidden' tag, such as "Google Docs
    Domain Restriction". toggle it on and off.
 2. as a root account admin B with no site admin privileges,
    confirm the feature is not visible on the Features tab
    of the root account
 3. as site admin user A, visit the root account's Features
    tab and confirm the hidden feature is visible (with the
    "hidden" tag). turn it on.
 4. confirm that B sees the feature on the root account's
    Features tab
 5. as A, turn the feature back off in B's account settings
    (not site admin settings)
 6. confirm that, after a page reload, B can no longer see
    the feature on the root account's Features tab

fixes CNVS-16251

Change-Id: I2e1bebe1e710471f2a0efeb8e744cabddee89df8
Reviewed-on: https://gerrit.instructure.com/45751
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>