Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/73732100eb27
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18432 from zbraniecki/995425-upgrade-sinon

Bug 995425 - upgrade sinon to 1.9.1 and update API usage. r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/d49ecdeb839b
Author: Zbigniew Braniecki <gandalf@mozilla.com>
Desc: Bug 995425 - upgrade sinon to 1.9.1 and update API usage. r=julienw

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https://hg.mozilla.org/integration/gaia-central/rev/14bb54bbc478
Author: Dale Harvey <dale@arandomurl.com>
Desc: Bug 997680 - Show a google search link if exists in e.me results. r=kgrandon
Bumping manifests a=b2g-bump