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

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https://hg.mozilla.org/integration/gaia-central/rev/7940b793eddf
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #26167 from KevinGrandon/bug_1100153_browser_chrome_gap

Bug 1100153 - Gap between browser chrome and app window

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https://hg.mozilla.org/integration/gaia-central/rev/54bae4673be2
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1100153 - Gap between browser chrome and app window r=Cwiiis
Bumping manifests a=b2g-bump