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

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https://hg.mozilla.org/integration/gaia-central/rev/66957146e0a3
Author: Vivien Nicolas <21@vingtetun.org>
Desc: Bug 967440 - Remove some reflows on the keypad. r=Rik
Bumping manifests a=b2g-bump