converts users/index js_block into js_bundle

test plan:
* regression test user index

Change-Id: I514ebef4be0ee0e42c2ad5607da330010dd8a832
Reviewed-on: https://gerrit.instructure.com/29094
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: Matt Fairbourn <mfairbourn@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>