Display correct RCE border color for High Contrast UI
Display correct RCE border color for High Contrast UI

closes MAT-836

flag=None

test plan:
-turn on High Contrast UI
-find an RCE
-click inside the RCE to get it to focus mode
-observe that the border is now  #0770A3 (blue)

Change-Id: Icd0cc3dfa5e5e06366dfdf2310c867dc290852c8
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/295486
Reviewed-by: Jake Oeding <9601d161174d3602f0f7ee77da5115e75d23bb40@instructure.com>
QA-Review: Jake Oeding <9601d161174d3602f0f7ee77da5115e75d23bb40@instructure.com>
Product-Review: David Lyons <c345b6495d82f574bde007a1165ad87fad2909cd@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>

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