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

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https://hg.mozilla.org/integration/gaia-central/rev/5cc15d1e2910
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #13960 from KevinGrandon/bug_942235_gaia_extension_logging

Bug 942235 - Remove errors being logged from gaia extensions r=vingtetun

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https://hg.mozilla.org/integration/gaia-central/rev/30315c0f189a
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 942235 - Remove errors being logged from gaia extensions
Bug 910456 - fix test_lastModificationFilter.html to verify timestamps when creating test files. r=janv

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extra : rebase_source : a128af8ab386767b4255c50aa4d78c5b3d146849