converts rubrics/index js_block into js_bundle

test plan:
* regression test rubrics

Change-Id: I61810f5c2c00f3614008f19ca31d243cd483fca4
Reviewed-on: https://gerrit.instructure.com/29133
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>