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

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https://hg.mozilla.org/integration/gaia-central/rev/6321667311ff
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Merge pull request #12080 from fabi1cazenave/systemMissingEntities-bug914626

Bug 914626: [System] missing entities, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/522f9735b042
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Bug 914626: [System] missing entities, r=steveck