add url to New Quizzes FF
add url to New Quizzes FF

closes QUIZ-8838
flag=quizzes_next

test plan:
 - the New Quizzes feature flag should have an updated
   description, including a link to the New Quizzes
   community group

Change-Id: If82d3b9aacd0a0ddf371c5c2a1177715328ea253
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/275327
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Jorge Arteaga <797aca0b58c1608d2f0b1cb4d451b10108621a94@instructure.com>
QA-Review: Mark McDermott <20dd8ba615f2257ea7254f93d6f30ae11aa4f904@instructure.com>
Product-Review: Susan Sorensen <0d98e282ba669db948aa8e61bd608c56b3926d27@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms