change 'switch gradebooks' links text

fixes CNVS-13004

test plan:
 - in gb2, click the 'Switch to Individual View' link
 - srgb should now be your default gb view
 - in srgb, click the 'Switch to Grid View' link
 - gb2 should now be your default gb view

Change-Id: Ib747e31802590d8a556a688bc2bf02b266f54928
Reviewed-on: https://gerrit.instructure.com/34772
Reviewed-by: Mike Nomitch <mnomitch@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Anna Koalenz <akoalenz@instructure.com>