Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/449764bc60ba
Author: Hubert Figuière <hub@figuiere.net>
Desc: Revert gaia integration breake since bug 917717. a=bustage

exec-sync NodeJS module fail to build.