Bumping gaia.json for 2 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/57210698c630
Author: Albert <acperez@tid.es>
Desc: Merge pull request #11922 from acperez/bug-911809

Bug 911809 - Copy variant.json at build-time to ftu. r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/db5682948b30
Author: Albert <acperez@tid.es>
Desc: Bug 911809 - Copy variant.json at build-time to ftu. r=yurenju