Add 'New Quizzes Banks Migrations' SiteAdmin FF
Add 'New Quizzes Banks Migrations' SiteAdmin FF

closes QUIZ-8260
flag=none

Test plan
- Verify the feature flag 'New Quizzes Banks Migrations' is
visible only to site admin

Change-Id: I6471dd17fff69772f8a3d76577ff4061816506d5
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/263014
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Product-Review: Jorge Arteaga <797aca0b58c1608d2f0b1cb4d451b10108621a94@instructure.com>
Reviewed-by: Jared Crystal <06625ed3fabb97fffd807b5fd3c4e9314fe77676@instructure.com>
QA-Review: Mark McDermott <20dd8ba615f2257ea7254f93d6f30ae11aa4f904@instructure.com>

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