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

========

https://hg.mozilla.org/integration/gaia-central/rev/14b730ec837b
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #16436 from timdream/system2-hardwarebuttons-fix

Bug 974261 - Volume buttons stucks, need clearTimeout() +shepherd

========

https://hg.mozilla.org/integration/gaia-central/rev/78ffacdc778c
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 974261 - Volume buttons stucks, need clearTimeout()
Bumping manifests a=b2g-bump