update link on canvas app page

fixes PLAT-534

test-plan:

the link in Canvas Apps page should go to eduappcenter.com instead of edu-apps.org

Change-Id: I65ea243e017573e6ad97398c56815ba62dc1a8fb
Reviewed-on: https://gerrit.instructure.com/37781
Reviewed-by: Brad Humphrey <brad@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Nathan Mills <nathanm@instructure.com>