Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-2_0/rev/4d6e941e173e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1043870 - Disable intermittent failing test, TEST-UNEXPECTED-FAIL | /builds/slave/test/gaia/apps/system/test/marionette/homescreen_navigation_test.js | Homescreen navigation > Going to the homescreen and back to a warm app r=kgrandon a=npotb
Bumping manifests a=b2g-bump