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

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https://hg.mozilla.org/integration/gaia-central/rev/af6b88994605
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #12125 from PinZhang/bug915082_bookmark_icon

Bug 915082 - Replace favorite icons, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/069247fe83bc
Author: pzhang <pzhang@mozilla.com>
Desc: Bug 915082 - Replace favorite icons