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

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https://hg.mozilla.org/integration/gaia-central/rev/1509497bd4b5
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #13881 from AntonioMA/bug936018

Bug 936018 - Change the way the icons are loaded to allow reentrant calls

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https://hg.mozilla.org/integration/gaia-central/rev/c2e1c7aed6f3
Author: Antonio M. Amaya <amac@peregrin>
Desc: Bug 936018 - Change the way the icons are loaded to allow reentrant calls