convert courses/show js_block into js_bundle

test plan:
* regression test course show page

Change-Id: Ic80d5c718496fb0cf7e36044606275f6dca9c43b
Reviewed-on: https://gerrit.instructure.com/29156
Reviewed-by: Jon Jensen <jon@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Landon Wilkins <lwilkins@instructure.com>