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

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https://hg.mozilla.org/integration/gaia-central/rev/bb821fbbbdd5
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #10964 from crh0716/893625

Bug 893625 - Support hdpi resolution device and add 1.5x assets r=dkuo

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https://hg.mozilla.org/integration/gaia-central/rev/e95392a95276
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 893625 - Support hdpi resolution device and add 1.5x assets