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

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https://hg.mozilla.org/integration/gaia-central/rev/a28d5864a243
Author: Alexandre Lissy <lissyx+github@lissyx.dyndns.org>
Desc: Revert "Merge pull request #12911 from lissyx/bug906296"

This reverts commit b9520ca7b28e469c91efd851e7af9ad7b38ee3ed, reversing
changes made to bc2fb252092af20050551ecbd7c5a3edab77b58e.