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

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https://hg.mozilla.org/integration/gaia-central/rev/6c593455e3d1
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #17786 from KevinGrandon/bug_989663_contacts_jshint

Bug 989663 - [Contacts] Jshint fixes for js/ r=arcturus

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https://hg.mozilla.org/integration/gaia-central/rev/410ade2be66a
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 989663 - [Contacts] Jshint fixes for js/ r=arcturus
Bumping manifests a=b2g-bump