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

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https://hg.mozilla.org/integration/gaia-central/rev/0a6ca1097038
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Merge pull request #12292 from basiclines/settings-highlights

Bug 917704 - Use Full Line Highlights in Settings, r=kaze

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https://hg.mozilla.org/integration/gaia-central/rev/c52bf9c5c134
Author: basiclines <igonzaleznicolas@gmail.com>
Desc: Bug 917704 - Use Full Line Highlights in Settings