switch youtube embeds to use iframes
switch youtube embeds to use iframes

fixes CNVS-30980

Object embeds recently stopped working in Chrome.  This might just be
a bug in Chrome, or it might be the beginning of them rolling out their
plan to stop loading flash by default for most websites.  Either way,
this embed method has been deprecated for a while, it's time to switch.

Test plan:
- regression test embedding youtube links, specifically around playing
them as a viewing user

Change-Id: Idf251fdd6c097e16048f32461ea2e5286005f299
Reviewed-on: https://gerrit.instructure.com/87966
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Tested-by: Jenkins
QA-Review: Benjamin Christian Nelson <4a283f6b032925e40a485c88ede5597d7d65a090@instructure.com>
Product-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>

grahamb/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,SwinburneOnline/canvas-lms,venturehive/canvas-lms,venturehive/canvas-lms,SwinburneOnline/canvas-lms,SwinburneOnline/canvas-lms,HotChalk/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,venturehive/canvas-lms,djbender/canvas-lms,grahamb/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,HotChalk/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,HotChalk/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,sfu/canvas-lms