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

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https://hg.mozilla.org/integration/gaia-central/rev/489f90bf6291
Author: Albert <acperez@tid.es>
Desc: Merge pull request #11859 from acperez/bug-904006

Bug 904006 - Build process customization for operator apps. r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/4283880603ad
Author: Albert <acperez@tid.es>
Desc: Bug 904006 - Build process customization for operator apps