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

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https://hg.mozilla.org/integration/gaia-central/rev/1560239ea718
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20476 from KevinGrandon/bug_1024874_system_uuid

Bug 1024874 - [System] Use shared uuid.js

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https://hg.mozilla.org/integration/gaia-central/rev/125b019fa079
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1024874 - [System] Use shared uuid.js r=timdream
Bumping manifests a=b2g-bump