Bumping gaia.json for 2 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/173c47bee88e
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Merge pull request #13521 from fabi1cazenave/reducePaddings-bug927785

Bug 927785 - Reduce paddings in the Settings lists, r=arthurcc

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https://hg.mozilla.org/integration/gaia-1_2/rev/505021ba4019
Author: Fabien Cazenave <fabien@cazenave.cc>
Desc: Bug 927785 - Reduce paddings in the Settings lists