let other stuff run before trying to preload RCE
let other stuff run before trying to preload RCE

Test plan:
* if you go to the syllabus page, instead of seeing something like
  This https://cl.ly/855060b6ad3e where preloading the remote RCE module
  happens and executes before all the rest of the important js to render
  the the page
* you should instead see that preloadRemoteModule chunk of code happen
  later in a “Fire Idle Callback” task

Change-Id: I86a5d8579da3bdee5980a1ad5037ec85534c7f2a
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/213454
Tested-by: Jenkins
Reviewed-by: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
QA-Review: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
Product-Review: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>

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