converts submissions/show_preview js_blocks into js_bundles

test plan:
* regression test submissions show preview
** specifically for submission_type =
** media_recording, online_text_entry or online_upload

Change-Id: I6926b2709bcd5d2466c8ffc80d396c04d2212a3d
Reviewed-on: https://gerrit.instructure.com/29104
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jon Jensen <jon@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>