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

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https://hg.mozilla.org/integration/gaia-central/rev/553800a2a223
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #11611 from arcturus/bug-906123

Bug 906123 - The oninstall event handler of navigator.mozApps.mgmt fails on the Homescreen app with app.manifest is null r=crdlc

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https://hg.mozilla.org/integration/gaia-central/rev/934e77042bc4
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Bug 906123 - The oninstall event handler of navigator.mozApps.mgmt fails on the Homescreen app with app.manifest is null