remove all uses of compass functions

the last remaining uses of compass functions were
image-width and image-height

this gets rid of the remaining usage of those

...on our way to not needing compass at all

test plan:
nothing should change since all I did was replace
the scss with what the compiled css was

Change-Id: I0cd21a2dc193d7e154fb38acf11b841c9b2baaf8
Reviewed-on: https://gerrit.instructure.com/38329
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Colleen Palmer <colleen@instructure.com>
Product-Review: Ryan Shaw <ryan@instructure.com>
QA-Review: Ryan Shaw <ryan@instructure.com>