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

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https://hg.mozilla.org/integration/gaia-central/rev/6434a9e432b5
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #14410 from rnowm/946718

Bug 946718 - [SMS] When there's no messages, the header shows a shadow below

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https://hg.mozilla.org/integration/gaia-central/rev/30b0978059d5
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 946718 - [SMS] When there's no messages, the header shows a shadow below