hide the external link icon on the login page, again
hide the external link icon on the login page, again

closes MAT-1101
flag=none

test plan:
  - view the canvas login page
  > expect no external link icons to show

Change-Id: I93e89d117ad34d11d9dfb515ed095fcfdaa87115
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/305481
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Jake Oeding <9601d161174d3602f0f7ee77da5115e75d23bb40@instructure.com>
QA-Review: Jake Oeding <9601d161174d3602f0f7ee77da5115e75d23bb40@instructure.com>
Product-Review: Ed Schiebel <0ca8a83847a5889cf05cb219c0ab09f6b646243b@instructure.com>

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