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

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https://hg.mozilla.org/integration/gaia-central/rev/8160f6a0e58f
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #16384 from KevinGrandon/bug_941484_follow_up

Bug 941484 - [System2] Fix bootstrap test ordering

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https://hg.mozilla.org/integration/gaia-central/rev/9c47dd9176e0
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 941484 - [System2] Fix bootstrap test ordering
Bumping manifests a=b2g-bump