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

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https://hg.mozilla.org/integration/gaia-central/rev/59cd7c4ee453
Author: Salvador de la Puente González <salva@unoyunodiez.com>
Desc: Merge pull request #13552 from lodr/bug-912510-non-zero-values

Bug 912510 - Removing non zero placeholders

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https://hg.mozilla.org/integration/gaia-central/rev/31c942c4e450
Author: lodr <salva@unoyunodiez.com>
Desc: Bug 912510 - Removing non zero placeholders