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

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https://hg.mozilla.org/integration/gaia-central/rev/4d91a52faace
Author: Francisco Borja Salguero Castellano <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #12249 from reubenmorais/contacts-customization

Bug 891723 - Implement preloaded contacts customization by SIM

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https://hg.mozilla.org/integration/gaia-central/rev/5410f857e2a1
Author: Reuben Morais <reuben.morais@gmail.com>
Desc: Bug 891723 - Implement preloaded contacts customization by SIM. r=arcturus