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

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https://hg.mozilla.org/integration/gaia-central/rev/aa759fd2b573
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Merge pull request #11028 from jmcanterafonseca/merger_v1

Bug 889759 - Design and implement a ContactsMerger module

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https://hg.mozilla.org/integration/gaia-central/rev/975e1c00cf47
Author: Jose M. Cantera <jmcanterafonseca@gmail.com>
Desc: Bug 889759 - Design and implement a ContactsMerger module