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

========

https://hg.mozilla.org/integration/gaia-central/rev/3a5bfe8c6e07
Author: Mihai Cîrlănaru <mihai@cirlanaru.com>
Desc: Merge pull request #11497 from dylano/master

Bug 904115 - Add sr-Latn to languages_dev.json, r=@mcirlanaru

========

https://hg.mozilla.org/integration/gaia-central/rev/31b7f93dddf4
Author: dylano <doliver@mozilla.com>
Desc: Bug 904115 - Add sr-Latn to languages_dev.json