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

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https://hg.mozilla.org/integration/gaia-central/rev/b290b9fde0f1
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 902897 - Prevent e.me to be scrolled while panning between pages. r=ran

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https://hg.mozilla.org/integration/gaia-central/rev/56eadcdc815a
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 900989 - The height of homescreen pages force excessive repaints. r=ran

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https://hg.mozilla.org/integration/gaia-central/rev/3236858bec69
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 902465 - Too many CanvasLayer on e.me results hurt panning. r=ran

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https://hg.mozilla.org/integration/gaia-central/rev/fc6330d99b32
Author: Evyatar Amitay <evyatar@doat.com>
Desc: Bug 903043 - Fix and enhance e.me integration on the landing page. r=vingtetun