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

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https://hg.mozilla.org/integration/gaia-central/rev/6510f5901759
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #13785 from snowmantw/issue939434

Bug 939434 - Lock screen handle does not return to its original position when you hit "cancel" from passcode panel, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/fa584c25f86f
Author: Greg Weng <snowmantw@gmail.com>
Desc: Bug 939434 - Lock screen handle does not return to its original position when you hit "cancel" from passcode panel