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

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https://hg.mozilla.org/integration/gaia-central/rev/69612b1684ee
Author: Greg Weng <snowmantw@gmail.com>
Desc: Merge pull request #12291 from snowmantw/issue917689

Bug 917689 - LockScreen won't slide on B2G desktop and Firefox nightly

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https://hg.mozilla.org/integration/gaia-central/rev/df1f0f0ed60b
Author: Greg Weng <snowmantw@gmail.com>
Desc: Bug 917689 - LockScreen won't slide on B2G desktop and Firefox nightly