calendar: upgrade color-slicer

fixes CNVS-10351

test plan:
  * open calendar2
  * verify that calendar colors look more distinct than in
      http://screencast.com/t/PpKgnpPZ

Change-Id: I488acb1e16af4e51728aa11c3dd667025b11fbc4
Reviewed-on: https://gerrit.instructure.com/28261
Reviewed-by: Braden Anderson <banderson@instructure.com>
QA-Review: Braden Anderson <banderson@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Braden Anderson <banderson@instructure.com>