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

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https://hg.mozilla.org/integration/gaia-central/rev/4edbee2149a4
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Merge pull request #14884 from flodolo/bug950171

Bug 950171 - [settings] "Improve Firefox OS" title displayed as "Improve {{brandShortName}}"

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https://hg.mozilla.org/integration/gaia-central/rev/14fb92a7be15
Author: Francesco Lodolo (:flod) <flod@lodolo.net>
Desc: Bug 950171 - [settings] "Improve Firefox OS" title displayed as "Improve {{brandShortName}}"

Remove double substitution introduced in bug 944749, change string ID.