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

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https://hg.mozilla.org/integration/gaia-central/rev/4dff379346b2
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #17373 from crh0716/985090

Bug 985090 - Fix voicemail number migration issue and refactor r=jaoo

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https://hg.mozilla.org/integration/gaia-central/rev/4170f2f3c3e9
Author: Arthur Chen <crh0716@gmail.com>
Desc: Bug 985090 - Fix voicemail number migration issue and refactor
Bumping manifests a=b2g-bump