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

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https://hg.mozilla.org/integration/gaia-central/rev/e78fa2c8e1f3
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18302 from zbraniecki/995425-upgrade-sinon

Bug 995425 - Upgrade Sinon to 1.9.1 and update tests to match the API change

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https://hg.mozilla.org/integration/gaia-central/rev/7c77da41f0f7
Author: Zbigniew Braniecki <gandalf@mozilla.com>
Desc: Bug 995425 - Upgrade Sinon to 1.9.1 and update tests to match the API change. r=rexboy
Bumping manifests a=b2g-bump