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

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https://hg.mozilla.org/integration/gaia-central/rev/38aeb2b8ee6e
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #12315 from mcjimenez/bug893807

Bug 893807 - [User Story] Home screen adapted to operator apps in case o

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https://hg.mozilla.org/integration/gaia-central/rev/34ac87bd95d9
Author: Carmen Jimenez Cabezas <cjc@tid.es>
Desc: Bug 918432 - Operator apps are installed at a fixed position even when the SIM wasn't present at first boot