clean up conferences js

fixes CNVS-10195

test plan:
  * regression test conferences
      (I suggest you compare to beta)

Change-Id: Idd8f8fff6636509f00d87b83193c097339d5fd14
Reviewed-on: https://gerrit.instructure.com/28094
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Zach Pendleton <zachp@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Braden Anderson <banderson@instructure.com>