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

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https://hg.mozilla.org/integration/gaia-central/rev/55dad48c2099
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1105519 - merge pull request #26499 from KevinGrandon:bug_1105519_battery_overlay_strings to mozilla-b2g:master

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https://hg.mozilla.org/integration/gaia-central/rev/bb6df9503c2c
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1105519 - Remove strings from index.html for battery dialog r=kgrandon
Bumping manifests a=b2g-bump