Bumping gaia.json for 4 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/dbdd39110d1c
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: Merge pull request #12645 from EverythingMe/923445-grid-icons-alignment

[Bug 923445] Align grid icons on first page [r=crdlc]

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https://hg.mozilla.org/integration/gaia-central/rev/fdb7c0b8fbc4
Author: Evyatar Amitay <evyatron@gmail.com>
Desc: [Bug 923445] Align grid icons on first page [r=crdlc]

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https://hg.mozilla.org/integration/gaia-central/rev/25dc49bfa2fa
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #12651 from wanderview/contacts-notify-empty

Bug 923467: notifyAboveTheFold() when no contacts

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https://hg.mozilla.org/integration/gaia-central/rev/4b01ee152bb7
Author: Ben Kelly <ben@wanderview.com>
Desc: Bug 923467: notifyAboveTheFold() when no contacts