change the quiz export file extension
change the quiz export file extension

Test Plan:
 * Export quizzes for a course
 * The extensions should be .zip

closes #8248

Change-Id: I2a4b909c846ecd3690e34dcddf06e0dacc556cd5
Reviewed-on: https://gerrit.instructure.com/10171
Reviewed-by: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Tested-by: Hudson <dfb64870173313a9a7b56f814c8e3b33e268497a@instructure.com>

fronteerio/canvas-lms,wye0220/shindig-canvas,whalejasmine/canvas-lms,Rvor/canvas-lms,Jyaasa/canvas-lms,va7map/canvas-lms,nditech/red-innovadores-lms,redconfetti/canvas-lms,wye0220/shindig-canvas,ankithbti/canvas_lms,arrivu/qibla-ecampus,arrivu/arrivu-lms,greyhwndz/canvas-lms,wimemx/Canvas,usmschuck/canvas,jay3126/canvas-lms,landonwilkins/canvas-lms,HotChalk/canvas-lms,loganrun/pincan,nditech/red-innovadores-lms,arrivu/qibla-ecampus,arrivu/hoodemo,ankithbti/canvas_lms,merichar/canvas-lms,arrivu/jigsaw-lms,sdeleon28/canvas-lms,sfu/canvas-lms,antoniuslin/canvas-lms,leftplusrightllc/canvas-lms,sfu/canvas-lms,em2/canvas-lms,efrj/canvas-lms,juoni/canvas-lms,whalejasmine/canvas-lms,greyhwndz/canvas-lms,merichar/canvas-lms,antoniuslin/canvas-lms,redconfetti/canvas-lms,whalejasmine/canvas-lms,efrj/canvas-lms,utkarshx/canvas-lms,Unow/canvas-lms,sfu/canvas-lms,loganrun/pincan,nditech/red-innovadores-lms,sfu/canvas-lms,tgroshon/canvas-lms,rup/Tarrax,sli7246/canvas_branch,juoni/canvas-lms,landonwilkins/canvas-lms,jay3126/canvas-lms,redconfetti/canvas-lms,wye0220/shindig-canvas,antoniuslin/canvas-lms,arrivu/qibla-ecampus,shidao-fm/canvas-lms,tgroshon/canvas-lms,Jyaasa/canvas-lms,efrj/canvas-lms,venturehive/canvas-lms,Unow/ins,samuels410/greatlakes-lms,arrivu/arrivu-lms,grahamb/canvas-lms,usmschuck/canvas,grahamb/canvas-lms,nditech/red-innovadores-lms,sli7246/canvas_branch,Unow/canvas-lms,HotChalk/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,Rvor/canvas-lms,ShreniiNepal/shrenii_lmp,arrivu/arrivu-lms,tgroshon/canvas-lms,SwinburneOnline/canvas-lms,samuels410/greatlakes-lms,skmezanul/canvas-lms,usmschuck/canvas,Jyaasa/canvas-lms,landonwilkins/canvas-lms,HotChalk/canvas-lms,wrdsb/canvas-lms,parbros/red-innovadores-lms,juoni/canvas-lms,sfu/canvas-lms,Rvor/canvas-lms,Unow/ins,roxolan/canvas-lms,HotChalk/canvas-lms,va7map/canvas-lms,va7map/canvas-lms,skmezanul/canvas-lms,grahamb/canvas-lms,utkarshx/canvas-lms,wrdsb/canvas-lms,ankithbti/canvas_lms,kyroskoh/canvas-lms,kyroskoh/canvas-lms,venturehive/canvas-lms,leftplusrightllc/canvas-lms,fronteerio/canvas-lms,ShreniiNepal/shrenii_lmp,skmezanul/canvas-lms,Rvor/canvas-lms,arrivu/jigsaw-lms,fronteerio/canvas-lms,grahamb/canvas-lms,parbros/red-innovadores-lms,greyhwndz/canvas-lms,fronteerio/canvas-lms,rup/Tarrax,samuels410/greatlakes-lms,shidao-fm/canvas-lms,antoniuslin/canvas-lms,greyhwndz/canvas-lms,tgroshon/canvas-lms,Jyaasa/canvas-lms,merichar/canvas-lms,djbender/canvas-lms,usmschuck/canvas,venturehive/canvas-lms,shidao-fm/canvas-lms,sdeleon28/canvas-lms,wimemx/Canvas,Unow/ins,SwinburneOnline/canvas-lms,utkarshx/canvas-lms,wimemx/Canvas,venturehive/canvas-lms,shidao-fm/canvas-lms,rup/Tarrax,djbender/canvas-lms,redconfetti/canvas-lms,jay3126/canvas-lms,skmezanul/canvas-lms,leftplusrightllc/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,leftplusrightllc/canvas-lms,sdeleon28/canvas-lms,roxolan/canvas-lms,em2/canvas-lms,loganrun/pincan,sfu/canvas-lms,kyroskoh/canvas-lms,kyroskoh/canvas-lms,jay3126/canvas-lms,sfu/canvas-lms,Unow/canvas-lms,djbender/canvas-lms,arrivu/hoodemo,roxolan/canvas-lms,wrdsb/canvas-lms,juoni/canvas-lms,ShreniiNepal/shrenii_lmp,utkarshx/canvas-lms,whalejasmine/canvas-lms,efrj/canvas-lms,arrivu/hoodemo,SwinburneOnline/canvas-lms,em2/canvas-lms,ShreniiNepal/shrenii_lmp,parbros/red-innovadores-lms,landonwilkins/canvas-lms,sli7246/canvas_branch,wrdsb/canvas-lms,samuels410/greatlakes-lms,sdeleon28/canvas-lms,va7map/canvas-lms,arrivu/jigsaw-lms