Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/df0b1e4b8e67
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Revert "Merge pull request #16435 from evanxd/bug-973876"

This reverts commit 447eb65ee5a7428e3959ac3b1c0a3fbbfc125d43, reversing
changes made to 6894b915ee7d031a1f0ed16c422c48f293de1b84.
Bumping manifests a=b2g-bump