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

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https://hg.mozilla.org/integration/gaia-central/rev/dc99df54c60c
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #16130 from timdream/build-appdata-settings

Bug 968688 - Build sensors.json and support.json with settings/Makefile, r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/b1f7a9c297cc
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 968688 - Build sensors.json and support.json with settings/Makefile
Bumping manifests a=b2g-bump