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

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https://hg.mozilla.org/integration/gaia-central/rev/e479566bf0ea
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #11515 from gaye/bug-904830

Bug 904830 - Depend on marionette js helper in gaia a=test-only

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https://hg.mozilla.org/integration/gaia-central/rev/23302197b3f4
Author: gaye <gaye@mozilla.com>
Desc: Bug 904830 - Depend on marionette js helper in gaia a=test-only