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

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https://hg.mozilla.org/integration/gaia-central/rev/0848cbe74b41
Author: Ryan VanderMeulen <ryanvm@gmail.com>
Desc: Revert "Merge pull request #17072 from KevinGrandon/bug_971497_system2_home_gesture_2"

This reverts commit 632f28b224582b77dac0c70aa78ed171347b62af, reversing
changes made to 09c69607071109a9fa9a5831acde7f66df0ba8d0.
Bumping manifests a=b2g-bump