Revert "Bug 983080 - Add 2.25x icons to settings app"

This reverts commit feacb6e2a6b1b36af11f246641612cccc77426e5.
Bug 983080 - Add 2.25x icons to settings app
Bug 982260 - Gaia-integration tests on TBPL fail with: TEST-UNEXPECTED-FAIL | Contacts > Details Merging 15 contacts