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

========

https://hg.mozilla.org/integration/gaia-central/rev/12e1f6c57107
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #14676 from TheoChevalier/setringtone-reused-strings

Bug 950469 - [Setringtone][l12y] 'Set as ringtone' string is reused on t...

========

https://hg.mozilla.org/integration/gaia-central/rev/3227446feb9a
Author: TheoChevalier <theo.chevalier11@gmail.com>
Desc: Bug 950469 - [Setringtone][l12y] 'Set as ringtone' string is reused on title and button