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

========

https://hg.mozilla.org/integration/gaia-central/rev/1c9f7f3876d1
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #17849 from guilherme-pg/findmydevice

Bug 938896 - Find My Device client.

========

https://hg.mozilla.org/integration/gaia-central/rev/b9d78d517a99
Author: Guilherme Goncalves <guilherme.p.gonc@gmail.com>
Desc: Bug 938896 - Find My Device client.
Bumping manifests a=b2g-bump