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

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https://hg.mozilla.org/integration/gaia-central/rev/8a029e60aa29
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #20907 from KevinGrandon/bug_1028670_pre_intalled_collection_type

Bug 1028670 - [Collection app] Preinstalled SCs are ignored by app population and SC list

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https://hg.mozilla.org/integration/gaia-central/rev/6d92aeb3914f
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1028670 - [Collection app] Preinstalled SCs are ignored by app population and SC list r=crdlc r=ranbena
Bumping manifests a=b2g-bump