A11y: Fixed issue with JQueryUI tabs and NVDA

fixes CNVS-15755

Test plan:
- Using NVDA in FireFox visit the course settings page
- Verify that pressing enter on any tab will select that tab.
- Verify the same on other pages that use tabs.
- Verify the above with Jaws in IE and Safari with VO

Change-Id: I258e932aa325051b41228681d7588d599dfd54d5
Reviewed-on: https://gerrit.instructure.com/42813
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
Product-Review: Aaron Cannon <acannon@instructure.com>