Remove sandbox from File Preview iframe
Remove sandbox from File Preview iframe

Turns out it needs same-origin, and having both
same origin and allow-scripts basically makes the
sandboxing useless against security threats.

Removing the sandboxing will fix this issue.
Something is going to have to be figured out
when it comes to security, but that will have to
wait for another day.

Test plan:
Upload a docx file to canvas
Open the file preview
It should load correctly

Closes CNVS-49923

flag=none

Change-Id: I6af088d811c5371c50fc320df86333310fe5f5e0
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/245045
Reviewed-by: James Williams <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>
QA-Review: James Williams <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>
Product-Review: James Williams <3a5f4ed991dbfa5c9ef76ad729d240ca12f62180@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms