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

========

https://hg.mozilla.org/integration/gaia-central/rev/b6246e059f4f
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #15551 from waynux/issue936398

Bug 936398 - [Settings] Title wording r=crh0716

========

https://hg.mozilla.org/integration/gaia-central/rev/bcb5412c36d1
Author: Tzu-Wen Lin <wayne2833@gmail.com>
Desc: Bug 936398 - [Settings] Title wordings
Bumping manifests a=b2g-bump