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

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https://hg.mozilla.org/integration/gaia-central/rev/a8e6d298564a
Author: John Ford <john@johnford.info>
Desc: Revert "Merge pull request #14632 from alivedise/bugzilla/948596_v2/activity-window-size-copy"

This reverts commit 888f9df5515a47d2f5806efee77485e05e1e5416, reversing
changes made to 53b010647062b4e2637f98ac3538af1c7bfe723a.

This was backed out because of https://bugzilla.mozilla.org/show_bug.cgi?id=950136#c11