Bumping gaia.json for 2 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/6aa634c1f710
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #11544 from crh0716/905558

Bug 905558 - Toggle calls if there is an incoming call r=etienne a=leo+

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https://hg.mozilla.org/integration/gaia-central/rev/4a7ce6079028
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 905558 - Perform operations on active call at first, fallback to the previous call if the active call is null