Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f27a899758c2
Author: Ran Ben Aharon <ran@ranbena.com>
Desc: Bug 929668 - [everything.me] Runaway allocations in homescreen app [r=crdlc,evyatron]