Makes clicking the courses menu link open the menu

fixes CNVS-15373

Test Plan:
  - Open Canvas
  - Click on the Courses (Courses & Groups) on the global
    navigation
  - The menu should open, rather than navigate to the courses
    page.

Change-Id: I52a8c9262d7779020fa54f2d642d23e030ef4cb3
Reviewed-on: https://gerrit.instructure.com/41035
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Braden Anderson <braden@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Product-Review: Cosme Salazar <cosme@instructure.com>