Bumping gaia.json for 2 gaia-1_3 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_3/rev/0296c122760b
Author: Fabien Cazenave <fabien@mozilla.com>
Desc: Merge pull request #15743 from fabi1cazenave/uplift-bug956942

Bug 956942 - updated icons for the 'organic' skin, uplift to v1.3

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https://hg.mozilla.org/integration/gaia-1_3/rev/62502b6a5382
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Bug 956942 - updated icons for the 'organic' skin, uplift to v1.3