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

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https://hg.mozilla.org/integration/gaia-central/rev/6054940e3ea8
Author: evanxd <itoyxd@gmail.com>
Desc: Merge pull request #10805 from evanxd/bug-881137-images

Bug 881137 - hdpi/xhdpi resolution assets and layout for Calendar app

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https://hg.mozilla.org/integration/gaia-central/rev/af72bec7563d
Author: Evan Xd <itoyxd@gmail.com>
Desc: Bug 881137 - Update the image files as 1.5 times bigger images.