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

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https://hg.mozilla.org/integration/gaia-central/rev/ade2ad496f35
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #17056 from crh0716/975918_1

Bug 975918 - Support DSDS for voice mail r=jaoo, etienne

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https://hg.mozilla.org/integration/gaia-central/rev/1cf578cedfa3
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 975918 - Support DSDS for voice mail
Bumping manifests a=b2g-bump