update behavior of "courses" link in main navigation.
update behavior of "courses" link in main navigation.

fixes #10453

link previously went to dashboard; now links to the "/courses"
page. this is consistent with the behavior of the assignments link
in the main nav, which links to the "/assignments" page.

test plan:
  * click the "Courses" link in the main navigation;
  * verify that it links to the "/courses" page.

Change-Id: I490fcf5bb9fdebb59aef3a3012a0855e37395886
Reviewed-on: https://gerrit.instructure.com/13575
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
Reviewed-by: Cameron Matheson <1d572acbfa68c7c6e541c7b840d6b622e5c0dc91@instructure.com>

tgroshon/canvas-lms,sdeleon28/canvas-lms,whalejasmine/canvas-lms,leftplusrightllc/canvas-lms,ShreniiNepal/shrenii_lmp,greyhwndz/canvas-lms,djbender/canvas-lms,gbleydon/canvas-lms,matematikk-mooc/canvas-lms,instructure/canvas-lms,rup/Tarrax,whalejasmine/canvas-lms,HotChalk/canvas-lms,tgroshon/canvas-lms,arrivu/arrivu-lms,sfu/canvas-lms,arrivu/qibla-ecampus,Rvor/canvas-lms,HotChalk/canvas-lms,roxolan/canvas-lms,narigone/canvas,whalejasmine/canvas-lms,samuels410/greatlakes-lms,sli7246/canvas_branch,leftplusrightllc/canvas-lms,tgroshon/canvas-lms,parbros/red-innovadores-lms,landonwilkins/canvas-lms,snehakachroo1/LSI_replica,fronteerio/canvas-lms,sfu/canvas-lms,redconfetti/canvas-lms,narigone/canvas,arrivu/qibla-ecampus,rup/Tarrax,roxolan/canvas-lms,utkarshx/canvas-lms,efrj/canvas-lms,SwinburneOnline/canvas-lms,usmschuck/canvas,sfu/canvas-lms,efrj/canvas-lms,ShreniiNepal/shrenii_lmp,antoniuslin/canvas-lms,wimemx/Canvas,usmschuck/canvas,antoniuslin/canvas-lms,eCNAP/CANVAS,samuels410/greatlakes-lms,dgynn/canvas-lms,sdeleon28/canvas-lms,ankithbti/canvas_lms,arrivu/hoodemo,loganrun/pincan,leftplusrightllc/canvas-lms,loganrun/pincan,shidao-fm/canvas-lms,venturehive/canvas-lms,HotChalk/canvas-lms,usmschuck/canvas,venturehive/canvas-lms,samuels410/greatlakes-lms,fronteerio/canvas-lms,wrdsb/canvas-lms,Jyaasa/canvas-lms,Jyaasa/canvas-lms,gbleydon/canvas-lms,Rvor/canvas-lms,dgynn/canvas-lms,rup/Tarrax,wimemx/Canvas,snehakachroo1/LSI_replica,sfu/canvas-lms,SwinburneOnline/canvas-lms,nditech/red-innovadores-lms,utkarshx/canvas-lms,wrdsb/canvas-lms,sli7246/canvas_branch,Rvor/canvas-lms,arrivu/qibla-ecampus,fronteerio/canvas-lms,dgynn/canvas-lms,grahamb/canvas-lms,matematikk-mooc/canvas-lms,va7map/canvas-lms,usmschuck/canvas,arrivu/arrivu-lms,parbros/red-innovadores-lms,ShreniiNepal/shrenii_lmp,Unow/ins,sdeleon28/canvas-lms,utkarshx/canvas-lms,va7map/canvas-lms,greyhwndz/canvas-lms,AndranikMarkosyan/lms,jay3126/canvas-lms,efrj/canvas-lms,tgroshon/canvas-lms,merichar/canvas-lms,roxolan/canvas-lms,kyroskoh/canvas-lms,arrivu/hoodemo,juoni/canvas-lms,efrj/canvas-lms,instructure/canvas-lms,juoni/canvas-lms,antoniuslin/canvas-lms,shidao-fm/canvas-lms,snehakachroo1/LSI_replica,snehakachroo1/LSI_replica,matematikk-mooc/canvas-lms,loganrun/pincan,instructure/canvas-lms,arrivu/hiring-site,ankithbti/canvas_lms,shidao-fm/canvas-lms,venturehive/canvas-lms,dgynn/canvas-lms,whalejasmine/canvas-lms,narigone/canvas,arrivu/hiring-site,djbender/canvas-lms,grahamb/canvas-lms,kyroskoh/canvas-lms,Jyaasa/canvas-lms,grahamb/canvas-lms,Unow/canvas-lms,sli7246/canvas_branch,narigone/canvas,juoni/canvas-lms,greyhwndz/canvas-lms,jay3126/canvas-lms,redconfetti/canvas-lms,juoni/canvas-lms,Unow/ins,utkarshx/canvas-lms,leftplusrightllc/canvas-lms,redconfetti/canvas-lms,skmezanul/canvas-lms,landonwilkins/canvas-lms,arrivu/arrivu-lms,grahamb/canvas-lms,arrivu/hoodemo,sfu/canvas-lms,sfu/canvas-lms,wye0220/shindig-canvas,venturehive/canvas-lms,AndranikMarkosyan/lms,landonwilkins/canvas-lms,Unow/canvas-lms,arrivu/jigsaw-lms,roxolan/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,eCNAP/CANVAS,nditech/red-innovadores-lms,Unow/ins,wimemx/Canvas,Rvor/canvas-lms,redconfetti/canvas-lms,AndranikMarkosyan/lms,arrivu/hiring-site,greyhwndz/canvas-lms,SwinburneOnline/canvas-lms,va7map/canvas-lms,AndranikMarkosyan/lms,ShreniiNepal/shrenii_lmp,HotChalk/canvas-lms,arrivu/jigsaw-lms,jay3126/canvas-lms,eCNAP/CANVAS,wye0220/shindig-canvas,antoniuslin/canvas-lms,skmezanul/canvas-lms,wrdsb/canvas-lms,shidao-fm/canvas-lms,skmezanul/canvas-lms,instructure/canvas-lms,nditech/red-innovadores-lms,wye0220/shindig-canvas,merichar/canvas-lms,ankithbti/canvas_lms,wrdsb/canvas-lms,nditech/red-innovadores-lms,landonwilkins/canvas-lms,sdeleon28/canvas-lms,Unow/canvas-lms,merichar/canvas-lms,SwinburneOnline/canvas-lms,arrivu/jigsaw-lms,Jyaasa/canvas-lms,va7map/canvas-lms,fronteerio/canvas-lms,jay3126/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,kyroskoh/canvas-lms,gbleydon/canvas-lms,grahamb/canvas-lms,skmezanul/canvas-lms,parbros/red-innovadores-lms,eCNAP/CANVAS,sfu/canvas-lms,kyroskoh/canvas-lms,djbender/canvas-lms,samuels410/greatlakes-lms,matematikk-mooc/canvas-lms