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

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https://hg.mozilla.org/integration/gaia-central/rev/a36df4782c67
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #11189 from crh0716/898937

Bug 898937 - Add background size to the thumb r=rexboy

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https://hg.mozilla.org/integration/gaia-central/rev/591a4783221c
Author: crh0716 <crh0716@gmail.com>
Desc: Bug 898937 - Add background size to the thumb