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

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https://hg.mozilla.org/integration/gaia-central/rev/839658be2f27
Author: vingtetun <21@vingtetun.org>
Desc: Merge pull request #21137 from vingtetun/bug1026792.followup

Bug 1026792 - [Rocketbar] Rocketbar search should be cancelled when the ...

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https://hg.mozilla.org/integration/gaia-central/rev/b79a4b34313b
Author: Vivien Nicolas <vnicolas@mozilla.com>
Desc: Bug 1026792 - [Rocketbar] Rocketbar search should be cancelled when the device sleeps, or gets locked. Followup. r=kgrandon
Bumping manifests a=b2g-bump