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

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https://hg.mozilla.org/integration/gaia-central/rev/4ed06e3278b2
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #17995 from sfoster/backout-959694

Revert "Merge pull request #16262 from benfrancis/959694-master"

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https://hg.mozilla.org/integration/gaia-central/rev/a0d2ff3d1531
Author: Sam Foster <sfoster@mozilla.com>
Desc: Revert "Merge pull request #16262 from benfrancis/959694-master"
Bumping manifests a=b2g-bump