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

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https://hg.mozilla.org/integration/gaia-1_3/rev/c4cb876c3981
Author: Mason Chang <mason@masonchang.com>
Desc: Merge pull request #15419 from changm/bug958318

bug 958318 - Optimize Settings App to find homescreen counts r=arthurcc