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

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https://hg.mozilla.org/integration/gaia-central/rev/778bda25ac73
Author: Marcus Cavanaugh <m@mcav.com>
Desc: Merge pull request #18337 from mcav/fix-alarm-volume-change

Bug 996739 - [Clock] Alarm volume control must change immediately when slider is moved. r=millermedeiros

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https://hg.mozilla.org/integration/gaia-central/rev/94a983f53432
Author: Marcus Cavanaugh <m@mcav.com>
Desc: [Clock] Alarm volume control must change immediately when slider is moved.
Bumping manifests a=b2g-bump