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

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https://hg.mozilla.org/integration/gaia-central/rev/d5288fdb345c
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Revert "Bug 917537 - Turn back on modify_event_test.js it was disabled because of intermittent failures"

This reverts commit 99479a8c5e487a3c8a5430ac3aab37f0e2d67a20.
Bumping manifests a=b2g-bump