Remove tabindex="0" from score column of grades summary
Remove tabindex="0" from score column of grades summary

Fixes CNVS-29540

Test plan:
* Load a student's grade summary page
* Tab through the elements, you should not reach the score column

Change-Id: I9eccb4d42a5d2962c8209bc9d330bc9911cacf55
Reviewed-on: https://gerrit.instructure.com/84493
Tested-by: Jenkins
Reviewed-by: Spencer Olson <7cc0890d6f1f70810a023e7173eca5724d6c8e49@instructure.com>
Reviewed-by: Jeremy Neander <20252aad5efdc666f083d82ab63ed0f9f72a043e@instructure.com>
QA-Review: Nathan Rogowski <2e8aa918660411855c6d44d5bb2da677aa033255@instructure.com>
Product-Review: Keith T. Garner <a1a80143a840c140f31c3495ebbd9ec906e09fed@instructure.com>

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