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

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https://hg.mozilla.org/integration/gaia-central/rev/e5875a1a8d1f
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #12806 from anah/bug924114

Bug 924114 - Migrate homescreen tests to use app objects

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https://hg.mozilla.org/integration/gaia-central/rev/98eb63f8b2fb
Author: Ana Hristova <ana.nikolaeva@gmail.com>
Desc: Bug 924114 - Migrate homescreen tests to use app objects