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

========

https://hg.mozilla.org/integration/gaia-central/rev/1f950280814e
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: Merge pull request #12682 from EverythingMe/bugfix-missing-collection-icons

[Bug 923803] Fix collection icons with missing app icons [r=ranbena]

========

https://hg.mozilla.org/integration/gaia-central/rev/ac675e62de1d
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: [Bug 923803] Fix collection icons with missing app icons [r=crdlc]