outcome gradebook: fix outcome details link

fixes CNVS-11330

test plan:
  * open outcome gradebook
  * hover on a column header
  * click on the details link
  * click on an outcome
  * click on its title
  * verify that the outcome information loads

Change-Id: I46e3096659d8dcea47778dea738b26c7ff6958ca
Reviewed-on: https://gerrit.instructure.com/31691
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Reviewed-by: Jon Willesen <jonw@instructure.com>
Product-Review: Braden Anderson <banderson@instructure.com>