Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/46fd8517a37d
Author: Fernando Jiménez Moreno <ferjmoreno@gmail.com>
Desc: Merge pull request #15692 from 6a68/settings-app-WIP-rebased

Bug 949051 - Add Firefox Accounts to Settings app r=arthurcc

========

https://hg.mozilla.org/integration/gaia-central/rev/50ebffbcedcc
Author: Jared Hirsch <ohai@6a68.net>
Desc: Bug 949051 - Add Firefox Accounts to Settings app, preffed off. r=arthurcc

========

https://hg.mozilla.org/integration/gaia-central/rev/455270093503
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #17251 from vingtetun/bug984153

Bug 984153 - Add a background color to the thread list |ul| element. r=s...

========

https://hg.mozilla.org/integration/gaia-central/rev/2a1ca89e8097
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 984153 - Add a background color to the thread list |ul| element. r=schung
Bumping manifests a=b2g-bump