Update default allowed attributes in RCE
Update default allowed attributes in RCE

Fixes MAT-338
flag=none

Test Plan:
Verify none of the removed attributes can be included
on elements created via the RCE html editors

Change-Id: I849973210e43e12b6d2a39f67346fcd5f3cda4e5
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/268846
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Gary Mei <4dff5ebcff9ed76793b70b9470ac64791a16ed11@instructure.com>
QA-Review: Gary Mei <4dff5ebcff9ed76793b70b9470ac64791a16ed11@instructure.com>
Product-Review: Weston Dransfield <e9203059795dc94e28a8831c65eb7869e818825e@instructure.com>

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