add labels to course visibility options
add labels to course visibility options

fixes CNVS-31302

Test Plan:
- In Safari with VoiceOver enabled, open the Settings page of a
  course
- Move VO focus to the Visibility combo box
- Note that the current value and "pop up button" is read, and
  the label is also read

Change-Id: Idc45f05e01297f4378c366f5675f76625cfde46f
Reviewed-on: https://gerrit.instructure.com/89401
Tested-by: Jenkins
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
QA-Review: Deepeeca Soundarrajan <5bcd4b623f00b7fc2942cd1c65c245b30a48a61f@instructure.com>
Product-Review: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>

dgynn/canvas-lms,sfu/canvas-lms,matematikk-mooc/canvas-lms,HotChalk/canvas-lms,venturehive/canvas-lms,matematikk-mooc/canvas-lms,SwinburneOnline/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,grahamb/canvas-lms,dgynn/canvas-lms,HotChalk/canvas-lms,sfu/canvas-lms,dgynn/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,HotChalk/canvas-lms,matematikk-mooc/canvas-lms,matematikk-mooc/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,SwinburneOnline/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,SwinburneOnline/canvas-lms,sfu/canvas-lms,HotChalk/canvas-lms,SwinburneOnline/canvas-lms,dgynn/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,instructure/canvas-lms,djbender/canvas-lms