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

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https://hg.mozilla.org/integration/gaia-central/rev/db540afcf32e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #21647 from tanay1337/master

Update README.md r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/971678f584c1
Author: Tanay Pant <tanay1337@gmail.com>
Desc: Update README.md
Bumping manifests a=b2g-bump