fix keyboard nav for insert canvas image from tinymce toolbar
fix keyboard nav for insert canvas image from tinymce toolbar

Fixes CNVS-34299

Test Plan:
In the RCS, Press Alt+F10.
Select Image.
Choose the Canvas Tab in the Modal
Go through the folder to an image.
Attempt to select the image with Space/Enter – Note that it now  populates.

Change-Id: I57010183bec81f7664059b37298edd391f5b32e6
Reviewed-on: https://gerrit.instructure.com/101671
Tested-by: Jenkins
Reviewed-by: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>
QA-Review: Dan Sasaki
Product-Review: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>

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