profile: fix round cropping border for settings page

fixes CNVS-12479

test plan:
  * enable avatars
  * open settings page
  * edit your avatar
  * select a file
  * verify that the cropping tool has a circular border

Change-Id: Ic0313d3ff2e7304c3b0a0e7c54d893d311199af6
Reviewed-on: https://gerrit.instructure.com/33397
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Joel Hough <joel@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Braden Anderson <banderson@instructure.com>