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

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https://hg.mozilla.org/integration/gaia-central/rev/cbff74c74ea4
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #25048 from timdream/screen-brightness-transition

Bug 1081426 - Move screen brightness transition control out of ScreenManager, r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/655ea98b8322
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 1081426 - Move screen brightness transition control out of ScreenManager
Bumping manifests a=b2g-bump