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

========

https://hg.mozilla.org/integration/gaia-central/rev/dda92f46902c
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #15187 from KevinGrandon/bug_958251_task_manager

Bug 958251 - Task Manager r=alive

========

https://hg.mozilla.org/integration/gaia-central/rev/aff5709851d7
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 958251 - Task Manager r=alive