Allow resizing of canvadocs iframe in RCE preview
Allow resizing of canvadocs iframe in RCE preview

refs RD-4328

Test plan:
- Create an assignment, and in the description include a file upload
- View the assignment, and click the "preview" button
- Confirm that the document preview is resizable

Change-Id: Ifbd130815ad8e675d5dfa1cd97fc7b489e8c83b9
Reviewed-on: https://gerrit.instructure.com/119482
Tested-by: Jenkins
QA-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>
Reviewed-by: Brent Burgoyne <bccf16d7abdd2611580b1cd7d7a6fcc150d619da@instructure.com>
Product-Review: Caleb Guanzon <54fa1f30d451e4f3c341a8f3c47c9215fd0be9c6@instructure.com>

sfu/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms