visualize focusing on a tree
visualize focusing on a tree

fixes CNVS-17257

when navgating a file tree, focus wouldn't visually show up on the ul
tree. This removes the css attribute preventing this from happening.

Test Plan

Given you are working on new files
And you are only using the keyboard
Then use tabs to navigate to the file folder directory
And you should see that the tree ul should have a focus highlight around it.

Change-Id: Ifacf64eef1f30af4e6f7611c5a21720b0e67978f
Reviewed-on: https://gerrit.instructure.com/45819
Reviewed-by: Dan Minkevitch <2591e5f46f28d303f9dc027d475a5c60d8dea17a@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
QA-Review: Nathan Rogowski <2e8aa918660411855c6d44d5bb2da677aa033255@instructure.com>
Product-Review: Matt Fairbourn <5f353e1c97bb9cc046b9db20beca0b9392f6f1b2@instructure.com>

skmezanul/canvas-lms,tgroshon/canvas-lms,leftplusrightllc/canvas-lms,va7map/canvas-lms,snehakachroo1/LSI_replica,Jyaasa/canvas-lms,narigone/canvas,Rvor/canvas-lms,eCNAP/CANVAS,venturehive/canvas-lms,utkarshx/canvas-lms,narigone/canvas,roxolan/canvas-lms,leftplusrightllc/canvas-lms,juoni/canvas-lms,tgroshon/canvas-lms,va7map/canvas-lms,juoni/canvas-lms,redconfetti/canvas-lms,dgynn/canvas-lms,ShreniiNepal/shrenii_lmp,skmezanul/canvas-lms,SwinburneOnline/canvas-lms,wrdsb/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,matematikk-mooc/canvas-lms,antoniuslin/canvas-lms,Rvor/canvas-lms,SwinburneOnline/canvas-lms,grahamb/canvas-lms,efrj/canvas-lms,greyhwndz/canvas-lms,samuels410/greatlakes-lms,skmezanul/canvas-lms,samuels410/greatlakes-lms,sdeleon28/canvas-lms,matematikk-mooc/canvas-lms,redconfetti/canvas-lms,dgynn/canvas-lms,antoniuslin/canvas-lms,fronteerio/canvas-lms,utkarshx/canvas-lms,snehakachroo1/LSI_replica,djbender/canvas-lms,HotChalk/canvas-lms,dgynn/canvas-lms,sfu/canvas-lms,sdeleon28/canvas-lms,jay3126/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,ShreniiNepal/shrenii_lmp,utkarshx/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,roxolan/canvas-lms,ShreniiNepal/shrenii_lmp,wrdsb/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,matematikk-mooc/canvas-lms,jay3126/canvas-lms,narigone/canvas,sfu/canvas-lms,samuels410/greatlakes-lms,grahamb/canvas-lms,venturehive/canvas-lms,tgroshon/canvas-lms,efrj/canvas-lms,whalejasmine/canvas-lms,Jyaasa/canvas-lms,SwinburneOnline/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,jay3126/canvas-lms,shidao-fm/canvas-lms,HotChalk/canvas-lms,leftplusrightllc/canvas-lms,ShreniiNepal/shrenii_lmp,AndranikMarkosyan/lms,fronteerio/canvas-lms,matematikk-mooc/canvas-lms,whalejasmine/canvas-lms,narigone/canvas,sfu/canvas-lms,Rvor/canvas-lms,roxolan/canvas-lms,greyhwndz/canvas-lms,utkarshx/canvas-lms,shidao-fm/canvas-lms,skmezanul/canvas-lms,djbender/canvas-lms,kyroskoh/canvas-lms,venturehive/canvas-lms,wrdsb/canvas-lms,HotChalk/canvas-lms,whalejasmine/canvas-lms,eCNAP/CANVAS,greyhwndz/canvas-lms,efrj/canvas-lms,sdeleon28/canvas-lms,Rvor/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,efrj/canvas-lms,AndranikMarkosyan/lms,roxolan/canvas-lms,tgroshon/canvas-lms,Jyaasa/canvas-lms,dgynn/canvas-lms,HotChalk/canvas-lms,redconfetti/canvas-lms,antoniuslin/canvas-lms,eCNAP/CANVAS,juoni/canvas-lms,shidao-fm/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,greyhwndz/canvas-lms,snehakachroo1/LSI_replica,sdeleon28/canvas-lms,djbender/canvas-lms,antoniuslin/canvas-lms,redconfetti/canvas-lms,sfu/canvas-lms,shidao-fm/canvas-lms,wrdsb/canvas-lms,snehakachroo1/LSI_replica,va7map/canvas-lms,Jyaasa/canvas-lms,leftplusrightllc/canvas-lms,jay3126/canvas-lms,juoni/canvas-lms,AndranikMarkosyan/lms,samuels410/greatlakes-lms,whalejasmine/canvas-lms,kyroskoh/canvas-lms,va7map/canvas-lms,kyroskoh/canvas-lms,AndranikMarkosyan/lms,grahamb/canvas-lms,kyroskoh/canvas-lms,eCNAP/CANVAS,instructure/canvas-lms