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

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https://hg.mozilla.org/integration/gaia-central/rev/8c2ad9ad3192
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #12545 from huchengtw-moz/camera/Bug_921921_deleted_picture_can_be_displayed

Bug 921921 - [Buri][Gallery][Camera]Deleted picture can be displayed in ..., r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/57651974223a
Author: John Hu <johu@mozilla.com>
Desc: Bug 921921 - [Buri][Gallery][Camera]Deleted picture can be displayed in the camera