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

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https://hg.mozilla.org/integration/gaia-central/rev/81c55d0a3083
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Revert "Bug 938208 - Write test to enable Power Save mode"

This reverts commit 8b0caa764db462e3a80f3cad77c7ae053f750935.