Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/371c13208a54
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #16329 from Joshua-S/bug-971704

[Bug 971704] - Clean up Wallpaper File Structure in Gaia

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https://hg.mozilla.org/integration/gaia-central/rev/9bde3c63ffbc
Author: Joshua Smith <joshua-smith@verizon.net>
Desc: Bug 971704 - Clean up Wallpaper File Structure in Gaia
Bumping manifests a=b2g-bump