converts users/admin_merge js_block into js_bundle

test plan:
* regression test users admin merge

Change-Id: I781115b754b5f13bbab440673b5eab2f62928465
Reviewed-on: https://gerrit.instructure.com/29098
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>