undo disabling of brandable-css in qunit
undo disabling of brandable-css in qunit

refs FOO-1116

a change in b80e36d slipped through when i didn't mean for it to where
we disable BrandableCSS.loadStylesheet* functions in the karma/qunit
suite.. this was necessary at some point until the solution merged in
52fe84d made it no longer necessary

test plan:: jenkins (Karma suite) passes

Change-Id: I08c3363efcf64f3be0cda85685cc9b210519cdd6
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/269667
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Charley Kline <05950d7e90ba5e3da323378368c22b3ffaaf6647@instructure.com>
QA-Review: Charley Kline <05950d7e90ba5e3da323378368c22b3ffaaf6647@instructure.com>
Product-Review: Charley Kline <05950d7e90ba5e3da323378368c22b3ffaaf6647@instructure.com>

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