Bumping gaia.json for 3 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/a7ba8a801011
Author: Salvador de la Puente González <salva@unoyunodiez.com>
Desc: Merge pull request #11687 from lodr/bug-903401-buttons

 Bug 903401 - Fixing markup and CSS
r=arcturus

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https://hg.mozilla.org/integration/gaia-central/rev/c57e348473fc
Author: lodr <salva@unoyunodiez.com>
Desc: More fixing

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https://hg.mozilla.org/integration/gaia-central/rev/d497ac5b9811
Author: lodr <salva@unoyunodiez.com>
Desc: Bug 903401 - Fixing markup and CSS