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

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https://hg.mozilla.org/integration/gaia-central/rev/b3587428e8e7
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #13331 from gaye/bug-934237

Bug 934237 - Clean up calendar marionette tests

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https://hg.mozilla.org/integration/gaia-central/rev/b4a8bb4e44ba
Author: Gareth Aye <gaye@mozilla.com>
Desc: Bug 934237 - Clean up calendar marionette tests