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

========

https://hg.mozilla.org/integration/gaia-central/rev/8fe46c360427
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Revert "Bug 921828 - (app-menu) [Window Management] Refactor ListMenu and move it to AppWindow + implement System Wide Menu if needed"

This reverts commit daa85b79824ccc71f122011ebc0b5f2104db6620.

Reverted due to linter errors.
Bumping manifests a=b2g-bump