update icons in navigation tab
update icons in navigation tab

Closes: COMMS-1795

Test plan:
- open course settings
- open the navigation tab
- view the more icon, aka three dots, instead of the cog icon
- disable a link and see how it still contains the more icon
- enable the link again and confirm more icon is still visible

Change-Id: If800483bdf5716fa81dc02a43d2bbdb8827e2b19
Reviewed-on: https://gerrit.instructure.com/173896
Tested-by: Jenkins
Reviewed-by: Steven Burnett <a0b450117c5d20a22d5c4d52bb8ae13adee003d8@instructure.com>
QA-Review: KC Naegle <9fbecd016338f9910821a8a5d5d0ae4fc9abfaa5@instructure.com>
Product-Review: Erin Hallmark <2a4b17b11682b229726079a631360cf016a43450@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms