Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/1224c74fa5be
Author: Sam Foster <sam@sam-i-am.com>
Desc: Merge pull request #23967 from sfoster/task-manager-bug-1065511

Bug 1065511 - guard against falsey unfilteredStack. r=etienne

========

https://hg.mozilla.org/integration/gaia-central/rev/5ec2d6e01654
Author: Sam Foster <sfoster@mozilla.com>
Desc: Bug 1065511 - guard against falsey unfilteredStack. r=etienne

* Fallback to using StackManager.getCurrent() in exitToApp
Bumping manifests a=b2g-bump