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

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https://hg.mozilla.org/integration/gaia-central/rev/4b8f2afe1cbd
Author: Mihai Cîrlănaru <mihai@cirlanaru.com>
Desc: Merge pull request #14235 from mihai/bug_944214

Bug 944214 - [Settings] Update list buttons to match BB. r=@crh0716

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https://hg.mozilla.org/integration/gaia-central/rev/89b751b8094d
Author: Mihai Cirlanaru <mihai@cirlanaru.com>
Desc: Bug 944214 - [Settings] Update PIN and lockscreen list buttons to use arrows. r=arthurcc