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

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https://hg.mozilla.org/integration/gaia-central/rev/4139202f5927
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #15798 from crdlc/bug-965056

Bug 965056 - [B2G] Home screen is navigable whilst in the set wallpaper ...

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https://hg.mozilla.org/integration/gaia-central/rev/e4568a1d4059
Author: crdlc <crdlc@tid.es>
Desc: Bug 965056 - [B2G] Home screen is navigable whilst in the set wallpaper menu
Bumping manifests a=b2g-bump