add focus outline to 2 discussion buttons
add focus outline to 2 discussion buttons

flag=none
fixes VICE-2872

- run "bundle exec rake css:compile"
- turn Discussion/Announcement redesign
feature flag OFF
- visit a discussion
- verify that as you tab to focus on the
"Unread" and "Show deleted replies buttons"
as shown on the ticket, you now see a focus
outline similar to the outline for "search entries"
field

Change-Id: I9f21912fa2b2c4708c97642dd2da7700d084e43b
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/296153
Reviewed-by: Drake Harper <798ef92bc86a79e8ff768a68dc0a5fcec1d51660@instructure.com>
Product-Review: Drake Harper <798ef92bc86a79e8ff768a68dc0a5fcec1d51660@instructure.com>
QA-Review: Chawn Neal <908eabd8c84ff6c7c139535b8d37802d58ad1683@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