Bumping gaia.json for 3 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/4d431ce17144
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Merge pull request #12903 from qdot/927642-more-tests

Bug 927642 - Fix dir/lang integration tests for notifications

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https://hg.mozilla.org/integration/gaia-central/rev/466eb10c49ec
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Bug 927642 - Fix dir/lang integration tests for notifications

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https://hg.mozilla.org/integration/gaia-central/rev/e0b66df61173
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: fetch notification items in single roundtrip to marionette server