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

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https://hg.mozilla.org/integration/gaia-central/rev/256e9b41093c
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #11163 from crdlc/bug-897418

Bug 897418

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https://hg.mozilla.org/integration/gaia-central/rev/4fa35c669c9f
Author: crdlc <crdlc@tid.es>
Desc: Bug 897418 - Merge Contacts: Implement UI for active merge when adding contact