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

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https://hg.mozilla.org/integration/gaia-central/rev/2617fca8036a
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #25282 from gaye/alarms-refactor

Bug 1042939 - Resurrect periodic sync, alarms refactor r=millermedeiros

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https://hg.mozilla.org/integration/gaia-central/rev/37edca27dedc
Author: gaye <gaye@mozilla.com>
Desc: Bug 1042939 - Resurrect periodic sync, alarms refactor
Bumping manifests a=b2g-bump