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

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https://hg.mozilla.org/integration/gaia-central/rev/4024e28dbc44
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Revert "Merge pull request #22001 from mikehenrty/bug-1038988-wallpaper-flatten"

This reverts commit 8abddb42a444dd165332e6642133932a04020b50, reversing
changes made to 90bb50d59cffda27e1bf035c9590a5f3062e4832.
Bumping manifests a=b2g-bump