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

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https://hg.mozilla.org/integration/gaia-central/rev/c406aed66b1a
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Merge pull request #11437 from jonallengriffin/updateui

Bug 866908 - Pick up a newer version of gaia-ui-tests, a=test-only

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https://hg.mozilla.org/integration/gaia-central/rev/d6110bb2ae9d
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Bug 866908 - Pick up a newer version of gaia-ui-tests, a=test-only