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

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https://hg.mozilla.org/integration/gaia-central/rev/d3b76729af3d
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #17999 from richierichrawr/patch-1

Edit tablet customization doc for readability r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/1ae9a46aa54a
Author: richierichrawr <richierichrawr@users.noreply.github.com>
Desc: Edit for readability

It was missing a few things.
Bumping manifests a=b2g-bump