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

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https://hg.mozilla.org/integration/gaia-central/rev/ffe1b4bf3d09
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #19854 from KevinGrandon/bug_1018699_create_gaia_checkbox

Bug 1018699 - Create gaia-checkbox web component

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https://hg.mozilla.org/integration/gaia-central/rev/4b8645533264
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1018699 - Create gaia-checkbox web component r=yor
Bumping manifests a=b2g-bump